Ion-sensitive, water-dispersible polymers, a method of making same and items using same

ABSTRACT

The present invention is directed to ion-sensitive, water-dispersible polymers. The present invention is also directed to a method of making ion-sensitive, water-dispersible polymers and their applicability as binder compositions. The present invention is further directed to fiber-containing fabrics and webs comprising ion-sensitive, water-dispersible binder compositions and their applicability in water-dispersible personal care products.

FIELD OF THE INVENTION

The present invention is directed to ion-sensitive, water-dispersiblepolymer formulations. The present invention is also directed to a methodof making ion-sensitive, water-dispersible polymer formulations andtheir applicability as binder compositions for disposable items. Thepresent invention is further directed to disposable items, such aswet-wipes comprising ion-sensitive, water-dispersible bindercompositions.

BACKGROUND OF THE INVENTION

For many years, the problem of disposability has plagued industrieswhich provide disposable items, such as, diapers, wet wipes, incontinentgarments and feminine care products. While much headway has been made inaddressing this problem, one of the weak links has been the inability tocreate an economical coherent fibrous web, which will readily dissolveor disintegrate in water, but still have sufficient in-use strength.See, for example, U.K. patent disclosure 2,241,373 and U.S. Pat. No.4,186,233. Without such a product, the ability of the user to dispose ofthe product by flushing it down the toilet is greatly reduced, if noteliminated. Furthermore, the ability of the product to disintegrate in alandfill is quite limited because a large portion of the productcomponents, which may well be biodegradable or photodegradable, areencapsulated in or bound together by plastic which degrades over a longperiod of time, if at all. Accordingly, if the plastic disintegrated inthe presence of water, the internal components could degrade as a resultof the rupture of the plastic encapsulation or binding.

Disposable products, such as diapers, feminine care products and adultincontinent care products may be made to be disposed by flushing downtoilets. Usually such products comprise a body side liner which mustrapidly pass fluids, such as urine or menses, so that the fluid may beabsorbed by an absorbent core of the product. Typically, the body sideliner may be a coherent fibrous web, which desirably possesses a numberof characteristics, such as softness and flexibility. The fibrous web ofthe body side liner material may be typically formed by wet or dry (air)laying a generally random plurality of fibers and joining them togetherto form a coherent web with a binder compositions. Past bindercompositions have preformed this function well. However, fibrous webscomprising these compositions tended to be non-dispersible and presentproblems in typical household sanitation systems.

Recent binder compositions have been developed which can be moredispersible and are more environmentally responsible than past bindercompositions. One class of binder compositions includes polymericmaterials having inverse solubility in water. These binder compositionsare insoluble in warm water, but are soluble in cold water, such asfound in a toilet. It is well known that a number of polymers exhibitcloud points or inverse solubility properties in aqueous media. Thesepolymers have been cited in several publications for variousapplications, including (1) as evaporation retarders (JP 6207162); (2)as temperature sensitive compositions, which are useful as temperatureindicators due to a sharp color change associated with a correspondingtemperature change (JP 6192527); (3) as heat sensitive materials thatare opaque at a specific temperature and become transparent when cooledto below the specific temperature (JP 51003248 and JP 81035703); (4) aswound dressings with good absorbing characteristics and easy removal (JP6233809); and (5) as materials in flushable personal care products (U.S.Pat. No. 5,509,913, issued to Richard S. Yeo on Apr. 23, 1996 andassigned to Kimberly-Clark Corporation).

Other recent binders of interest include a class of binders, which areion-sensitive. Several U.S. and European patents assigned to LionCorporation of Tokyo, Japan, disclose ion-sensitive polymers comprisingacrylic acid and alkyl or aryl acrylates. See U.S. Pat. Nos. 5,312,883,5,317,063 and 5,384,189, the disclosures of which are incorporatedherein by reference, as well as, European Pat. No. 608460A1. In U.S.Pat. No. 5,312,883, terpolymers are disclosed as suitable binders forflushable nonwoven webs. The disclosed acrylic acid-based terpolymers,which comprise partially neutralized acrylic acid, butyl acrylate and2-ethylhexyl acrylate, are suitable binders for use in flushablenonwoven webs in some parts of the world. However, because of thepresence of a small amount of sodium acrylate in the partiallyneutralized terpolymer, these binders fail to disperse in watercontaining more than about 15 ppm Ca²⁺ and/or Mg²⁺. When placed in watercontaining more than about 15 ppm Ca²⁺ and/or Mg²⁺ ions, nonwoven websusing the above-described binders maintain a tensile strength greaterthan 30 g/in, which negatively affects the “dispersibility” of the web.The proposed mechanism for the failure is that each calcium ion bindswith two carboxylate groups either intramolecularly or intermolecularly.Intramolecular association causes the polymer chain to coil up, whicheventually leads to polymer precipitation. Intermolecular associationyields crosslinking. Whether intramolecular or intermolecularassociations are taking place, the terpolymer is not soluble in watercontaining more than about 15 ppm Ca²⁺ and/or Mg²⁺. Due to the stronginteraction between calcium ions and the carboxylate groups of theterpolymer, dissociation of the complex is highly unlikely because thisassociation is irreversible. Therefore, the above-described polymer thathas been exposed to a high Ca²⁺ and/or Mg²⁺ concentration solution willnot disperse in water even if the calcium concentration decreases. Thislimits the application of the polymer as a flushable binder materialbecause most areas across the U.S. have hard water, which contains morethan 15 ppm Ca²⁺ and/or Mg²⁺.

In a co-pending application assigned to Kimberly Clark; i.e., U.S.patent application Ser. No. 09/223,999, filed Dec. 31, 1998 now U.S.Pat. No. 6,423,804, the disclosure of which is incorporated herein byreference, there is disclosed a modification of the acrylic acidterpolymers of the above-referenced patents to Lion Corporation.Specifically, U.S. patent application Ser. No. 09/223,999 now U.S. Pat.No. 6,423,884 discloses a sulfonate anion modified acrylic acidterpolymers which has improved dispersibility in relatively hard water;e.g., up to 200 ppm Ca²⁺ and/or Mg²⁺, compared to the unmodified Lionpolymers. However, the Lion Corporation ion-sensitive polymers of theabove-referenced patents and the sulfonate anion modified acrylic acidterpolymers of the co-pending application, when used as binders forpersonal care products, such as wet wipes, typically have reduced sheetwettability, increased sheet stiffness, increased sheet stickiness,reduced binder sprayability and relatively high product cost.

Another approach to dispersible personal care products is disclosed inU.S. Pat. No. 5,281,306 to Kao Corporation of Tokyo, Japan. This patentdiscloses a water-disintegratable cleansing sheet; i.e., wet wipe,comprising water-dispersible fibers treated with a water-soluble binderhaving a carboxyl group. The cleansing sheet is treated with a cleansingagent containing 5%-95% of a water-compatible organic solvent and 95%-5%water. A preferred organic solvent is propylene glycol. The cleansingsheet retains wet strength and does not disperse in the organicsolvent-based cleansing agent, but disperses in water.

Although many patents disclose various ion and temperature sensitivecompositions for water-dispersible or flushable materials, there existsa need for dispersible products possessing softness, flexibility, threedimensionality, and resiliency; wicking and structural integrity in thepresence of body fluids (including feces) at body temperature; and truefiber dispersion after toilet flushing so that fibers do not becomeentangled with tree roots or at bends in sewer pipes. In addition, theknown ion-sensitive polymers, such as those of Lion Corporation and theco-pending application of Kimberly Clark, have relatively highviscosities at high shear rates that make application by sprayingimpossible or impractical. Moreover, there is a need in the art forflushable products having water-dispersibility in all areas of theworld, including soft and hard water areas. Furthermore, there is a needfor water-dispersible binders that do not reduce wettability of productwith which they are used and are sprayable for easy and uniformapplication to and penetration into products. Finally, there is a needfor water-dispersible, flushable wet wipes that are stable duringstorage and retain a desired level of wet strength during use and arewetted with a wetting composition that is relatively free, or issubstantially free, of organic solvents. Such a product is needed at areasonable cost without compromising product safety and environmentalconcerns, something that past products have failed to do.

SUMMARY OF THE INVENTION

The present invention is directed to ion-sensitive polymer formulations,which have been developed to address the above-described problemsassociated with currently available, ion-sensitive polymers and otherpolymers described in literature. The ion-sensitive polymer formulationsof the present invention have a “trigger property,” such that thepolymers are insoluble in a wetting composition comprising ions of aparticular type and concentration, such as monovalent salt solutions ata concentration from about 0.3% to 10%, but can be soluble when dilutedwith water, including divalent salt solutions such as hard water with upto 200 ppm (parts per million) calcium and magnesium ions. Unlike someion-sensitive polymer formulations, which lose dispersibility in hardwater because of ion cross-linking by calcium ions, the polymerformulations of the present invention are relatively insensitive tocalcium and/or magnesium ions. Consequently, flushable productscontaining the polymer formulations of the present invention maintaindispersibility in hard water. Furthermore, the ion-sensitive polymerformulations of the present invention can have improved properties ofsprayability or reduced high-shear viscosity, improved productwettability or decreased properties of product stiffness and stickiness.

The polymer formulations of the present invention are useful as bindersand structural components for air-laid and wet-laid nonwoven fabrics forapplications such as body-side liners, fluid distribution materials,fluid in-take materials (surge) or cover stock in various personal careproducts. The polymer formulations of the present invention areparticularly useful as a binder material for flushable personal careproducts, particularly wet wipes for personal use such as cleaning ortreating skin, make-up removal, nail polish removal, medical care, andalso wipes for use in hard surface cleaning, automotive care, includingwipes comprising cleaning agents, disinfectants, and the like. Theflushable products maintain integrity or wet strength during storage anduse, and break apart or disperse after disposal in the toilet when thesalt concentration falls below a critical level. Suitable substrates fortreatment include tissue, such as creped or uncreped tissue, coformproducts, hydroentangled webs, airlaid mats, fluff pulp, nonwoven webs,and composites thereof. Methods for producing uncreped tissues andmolded three-dimensional tissue webs of use in the present invention canbe found in commonly owned U.S. patent application, Ser. No. 08/912,906,“Wet Resilient Webs and Disposable Articles Made Therewith,” by F. -J.Chen et al., filed Aug. 15, 1997; U.S. Pat. No. 5,429,686, issued toChiu et al. on Jul. 4, 1995; U.S. Pat. No. 5,399,412, issued to S. J.Sudall and S. A. Engel on Mar. 21, 1995; U.S. Pat. No. 5,672,248, issuedto Wendt et al. on Sep. 30, 1997; and U.S. Pat. No. 5,607,551, issued toFarrington et al. on Mar. 4, 1997; all of which are herein incorporatedin their entirety by reference. The molded tissue structures of theabove patents can be especially helpful in providing good cleaning in awet wipe. Good cleaning can also be promoted by providing a degree oftexture in other substrates as well by embossing, molding, wetting andthrough-air drying on a textured fabric, and the like.

Airlaid material can be formed by metering an airflow containing thefibers and other optional materials, in substantially dry condition,onto a typically horizontally moving wire forming screen. Suitablesystems and apparatus for air-laying mixtures of fibers andthermoplastic material are disclosed in, for example, U.S. Pat. No.4,157,724 (Persson), issued Jun. 12, 1979, and reissued Dec. 25, 1984 asRe. U.S. Pat. No. 31,775; U.S. Pat. No. 4,278,113 (Persson), issued Jul.14, 1981; U.S. Pat. No. 4,264,289 (Day), issued Apr. 28, 1981; U.S. Pat.No. 4,352,649 (Jacobsen et al.), issued Oct. 5, 1982; U.S. Pat. No.4,353,687 (Hosler, et al.), issued Oct. 12, 1982; U.S. Pat. No.4,494,278 (Kroyer, et al.), issued Jan. 22, 1985; U.S. Pat. No.4,627,806 (Johnson), issued Dec. 9, 1986; U.S. Pat. No. 4,650,409(Nistri, et al.), issued Mar. 17, 1987; and U.S. Pat. No. 4,724,980(Farley), issued Feb. 16, 1988; and U.S. Pat. No. 4,640,810 (Laursen etal.), issued Feb. 3, 1987.

The present invention also discloses how to make water-dispersiblenonwovens, including cover stock (liner), intake (surge) materials andwet wipes, which are stable in fluids having a first ionic composition,such as monovalent ions at a particular concentration substantiallygreater than is found in typical hard water, using the above-describedunique polymer formulations as binder compositions. The resultantnonwovens are flushable and water-dispersible due to the tailored ionsensitivity, which can be triggered regardless of the hardness of waterfound in toilets throughout the United States and the world. Dispersibleproducts in accordance with the present invention also can have improvedproperties of softness and flexibility. Such products also have reducedstickiness. In some embodiments, the polymer formulations with whichsuch articles are treated can have improved properties of sprayability,which improves polymer distribution on the product and penetration intothe product, in addition to ease of application, which translates intocost savings.

The present invention further discloses an improved wetting compositionfor wet wipes. Wet wipes employing the polymer formulations of thepresent invention are stable during storage and retain a desired levelof wet strength during use and are wetted with a wetting composition orcleaning agent that can be relatively free, or is substantially free, oforganic solvents.

These features and advantages of the present invention will becomeapparent after a review of the following detailed description of thedisclosed embodiments and the appended drawing and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph that depicts wet strength data for three binderformulations as a function of ionic environment and soak time.

FIG. 2 is a chart showing how wet tensile strength (reported as CDWT ingrams per 2.54 cm over a range of soak times) can change over time as afabric, comprising 68 gsm softwood airlaid webs and ion-sensitivebinders, are soaked in solutions comprising calcium ions.

FIG. 3 compares two data sets with Lion SSB-3b product taken from FIG. 2(labeled as Code 3300) with a sulfonated salt-sensitive binder blendedwith Dur-O-Set® RB polymer in a 75/25 ratio.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

In order to be an effective ion-sensitive formulations suitable for usein flushable or water-dispersible personal care products, theformulations should desirably be (1) functional; i.e., maintain wetstrength under controlled conditions and dissolve or disperse rapidly insoft or hard water such as found in toilets and sinks around the world;(2) safe (not toxic); and (3) relatively economical. In addition to theforegoing factors, the ion-sensitive formulations when used as a bindercomposition for a non-woven substrate, such as a wet wipe, desirablyshould be (4) processable on a commercial basis; i.e., may be appliedrelatively quickly on a large scale basis, such as by spraying, whichthereby requires that the binder composition have a relatively lowviscosity at high shear; (5) provide acceptable levels of sheet orsubstrate wettability; and (6) provide improved product feel, such asimproved product flexibility and reduced stickiness. The wettingcomposition with which the wet wipes of the present invention aretreated can provide some of the foregoing advantages, and, in addition,can provide one or more of (7) improved skin care, such as reduced skinirritation or other benefits, (8) improved tactile properties, and (9)promote good cleaning by providing a balance in use between friction andlubricity on the skin (skin glide). The ion-sensitive polymerformulations of the present invention and articles made therewith,especially wet wipes comprising particular wetting compositions setforth below, can meet many or all of the above criteria. Of course, itis not necessary for all of the advantages of the preferred embodimentsof the present invention to be met to fall within the scope of thepresent invention.

The polymer formulations of the present invention may be formed from asingle triggerable polymer, such as an ion-sensitive polymer, or from acombination of two or more different polymers, such as a triggerablepolymer and a co-binder. Desirably, at least one polymer of the polymerformulations of the present invention is an ion-sensitive polymer.Ion-sensitive polymers are known in the art and include any polymerwhose water solubility varies depending on the type and amount of ionspresent in water. Ion-sensitive polymers useful in the present inventioninclude, but are not limited to the Lion polymers discussed above, suchas the Lion acrylic acid terpolymer, the sulfonate anion modifiedacrylic acid terpolymer of the co-pending application 09/223,999 nowU.S. Pat. No. 6,423,884 assigned to Kimberly Clark Worldwide, Inc.; theacrylic acid free polymers of the co-pending U.S. patent applicationSer. No. 09/565,623, filed on May 4, 2000 now U.S. Pat. No. 6,537,663and entitled “Ion-Sensitive Hard Water Dispersible Polymers andApplications Therefor” (identified as KC No. 15851; J&A No. 11302-0481;Express Mail Label No. EL498682165US), also assigned to Kimberly ClarkWorldwide, Inc.; as well as, other ion- and chemical-sensitive polymers,including the polymers of U.S. Pat. No. 6,043,317, issued Mar. 28, 2000to Mumick et al., and also assigned to Kimberly Clark Worldwide, Inc.;the disclosures of which are herein incorporated by reference in theirentirety.

Other known triggerable polymers include temperature-sensitive andheat-sensitive polymers, as well as, polymers which become dispersiblein the presence of a dispersion aid added to the water of a toilet bowlor other water source, as discussed in U.S. Pat. No. 5,948,710, issuedSep. 7, 1999 to Pomplun et al. and assigned to Kimberly Clark Worldwide,Inc., who note that another means for rendering a polymer degradable inwater is through the use of temperature change. Certain polymers exhibita cloud point temperature. As a result, these polymers will precipitateout of a solution at a particular temperature, which is the cloud point.These polymers can be used to form fibers, which are insoluble in waterabove a certain temperature, but which become soluble and thusdegradable in water at a lower temperature. As a result, it is possibleto select or blend a polymer, which will not degrade in body fluids,such as urine, at or near body temperature (37° C.) but which willdegrade when placed in water at temperatures below body temperature, forexample, at room temperature (23° C). An example of such a polymer ispolyvinylmethylether, which has a cloud point of 34° C. When thispolymer is exposed to body fluids such as urine at 37° C., it will notdegrade as this temperature is above its cloud point (34° C.). However,if the polymer is placed in water at room temperature (23° C.), thepolymer will, with time, go back into solution as it is now exposed towater at a temperature below its cloud point. Consequently, the polymerwill begin to degrade. Blends of polyvinylmethylether and copolymers maybe considered as well. Other cold water soluble polymers includepoly(vinyl alcohol) graft copolymers supplied by the Nippon SyntheticChemical Company, Ltd. of Osaka, Japan, which are coded Ecomaty AX2000,AX10000 and AX300G.

Ion-Sensitive Polymers

The ion-sensitive Lion polymers and the ion-sensitive polymers of theabove-referenced co-pending applications and U.S. patents ofKimberly-Clark Worldwide, Inc. are useful in the present invention. Thesulfonate anion modified acrylic acid terpolymer of co-pending patentapplication Ser. No. 09/223,999, now U.S. Pat. No. 6,423,884 assigned toKimberly-Clark Worldwide, Inc., are desired because, unlike the LionCorp. polymers and other polymers cited in technical literature, thepolymers of the co-pending application 09/223,999 now U.S. Pat. No.6,423,884 are soluble in water having from less than about 10 ppm Ca²⁺and/or Mg²⁺ up to about 200 ppm Ca²⁺ and/or Mg²⁺. The polymers of theco-pending application are formulated to minimize the potentially stronginteraction between the anions of the polymers and the cations in thewater. This strong interaction can be explained via the hard-softacid-base theory proposed by R. G. Pearson in the Journal of theAmerican Chemical Society, vol. 85, pg. 3533 (1963); or N. S. Isaacs inthe textbook, Physical Organic Chemistry, published by LongmanScientific and Technical with John Wiley & Sons, Inc., New York (1987).Hard anions and hard cations interact strongly with one another. Softanions and soft cations also interact strongly with one another.However, soft anions and hard cations, and vice-versa, interact weaklywith one another. In the Lion polymers, the carboxylate anion of thesodium acrylate is a hard anion, which interacts strongly with the hardcations, Ca²⁺ and/or Mg²⁺, present in moderately hard and hard water. Byreplacing the carboxylate anions with a softer anion, such as asulfonate anion, the interaction between the anions of anion-triggerable polymer and the hard cations, Ca²⁺ and/or Mg²⁺, presentin moderately hard and hard water, is reduced.

As used herein, the term “soft water” refers to water having a divalention content of less than about 10 ppm. As used herein, the term“moderately hard water” refers to water having a divalent ion content offrom about 10 to about 50 ppm. As used herein, the term “hard water”refers to water having a divalent ion content of more than about 50 ppmup to about 200 ppm. By controlling the hydrophobic/hydrophilic balanceand the composition of the polymers as well as the combination ofpolymers forming the formulation, the ion-sensitive polymer formulationshaving desired in-use binding strength and water-dispersibility in waterare produced. The ion-sensitive polymer can be a copolymer, such as aterpolymer.

Ion-sensitive acrylic acid copolymers of the present invention maycomprise any combination of acrylic acid monomers and acrylic ester(alkyl acrylate) monomers capable of free radical polymerization into acopolymer and, specifically, a terpolymer. Suitable acrylic acidmonomers include, but are not limited to, acrylic acid and methacrylicacid. Suitable acrylic monomers include, but are not limited to, acrylicesters and methacrylic esters having an alkyl group of 1 to 18 carbonatoms or a cycloalkyl group of 3 to 18 carbon atoms and it is preferredthat acrylic esters and/or methacrylic esters having a alkyl group of 1to 12 carbon atoms or a cycloalkyl group of 3 to 12 carbon atoms be usedsingly or in combination. Other suitable monomers include, but are notlimited to, acrylamide and methacrylamide based monomers, such asacrylamide, N,N-dimethyl acrylamide, N-ethyl acrylamide, N-isopropylacrylamide, and hydroxymethyl acrylamide; N-vinylpyrrolidinone;N-vinylforamide; hydroxyalkyl acrylates and hydroxyalkyl methacrylates,such as hydroxyethyl methacrylate and hydroxyethyl acrylate. Othersuitable acrylic acid monomers and acrylic ester monomers are disclosedin U.S. Pat. No. 5,317,063, assigned to Lion Corporation, Tokyo, Japan,the disclosure of which is incorporated herein by reference in itsentirety. A particularly preferred acrylic acid terpolymer is LIONSSB-3b, available from Lion Corporation. (In alternative embodiments,the ion-sensitive polymer is formed from monomers other than acrylicacid or its derivatives, or is relatively free of acrylic acid,methacrylic acid, and salts thereof.)

The relative amounts of the monomers in the acrylic acid copolymer ofthe present invention may vary depending on the desired properties inthe resulting polymer. The mole percent of acrylic acid monomer in thecopolymer is up to about 70 mole percent. More specifically, the molepercent of acrylic acid monomer in the copolymer is from about 15 toabout 50 mole percent. Most specifically, the mole percent of acrylicacid monomer in the copolymer is from about 25 to about 40 mole percent.

More specifically, examples of the acrylic acid copolymers useful in thepresent invention include copolymers of 10 weight percent to 90 weightpercent, desirably 20 weight percent to 70 weight percent of acrylicacid and/or methacrylic acid and 90 weight percent to 10 weight percent,desirably 80 weight percent to 30 weight percent of acrylic estersand/or methacrylic esters having an alkyl group of 1 to 18 carbon atomsor a cycloalkyl group of 3 to 18 carbon atoms in which 1 to 60 molepercent, desirably 5 to 50 mole percent of acrylic acid and/ormethacrylic acid is neutralized to form a salt; or copolymers of 30weight percent to 75 weight percent, desirably 40 weight percent to 65weight percent of acrylic acid, 5 weight percent to 30 weight percent,desirably 10 weight percent to 25 weight percent of acrylic estersand/or methacrylic esters having an alkyl group of 8 to 12 carbon atomsand 20 weight percent to 40 weight percent; desirably 25 weight percentto 35 weight percent of acrylic esters and/or methacrylic esters havingan alkyl group of 2 to 4 carbon atoms in which 1 to 50 mole percent,desirably 2 to 40 mole percent of acrylic acid is neutralized to form asalt.

The acrylic acid copolymers of the present invention may have an averagemolecular weight, which varies depending on the ultimate use of thepolymer. The acrylic acid copolymers of the present invention have aweight average molecular weight ranging from about 10,000 to about5,000,000. More specifically, the acrylic acid copolymers of the presentinvention have a weight average molecular weight ranging from about25,000 to about 2,000,000, or, more specifically still, from about200,000 to about 1,000,000.

The acrylic acid copolymers of the present invention may be preparedaccording to a variety of polymerization methods, desirably a solutionpolymerization method. Suitable solvents for the polymerization methodinclude, but are not limited to, lower alcohols such as methanol,ethanol and propanol; a mixed solvent of water and one or more loweralcohols mentioned above; and a mixed solvent of water and one or morelower ketones such as acetone or methyl ethyl ketone.

In the polymerization methods of the present invention, anypolymerization initiator may be used. Selection of a particularinitiator may depend on a number of factors including, but not limitedto, the polymerization temperature, the solvent, and the monomers used.Suitable polymerization initiators for use in the present inventioninclude, but are not limited to, 2,2′-azobisisobutyronitrile,2,2′-azobis(2-methylbutyronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-amidinopropane)dihydrochloride,2,2′-azobis(N,N′-dimethyleneisobutylamidine), potassium persulfate,ammonium persulfate, and aqueous hydrogen peroxide. The amount ofpolymerization initiator may desirably range from about 0.01 to 5 weightpercent based on the total weight of monomer present.

The polymerization temperature may vary depending on the polymerizationsolvent, monomers, and initiator used, but in general, ranges from about20° C. to about 90° C. Polymerization time generally ranges from about 2to about 8 hours.

The sulfonate anion modified acrylic acid copolymers in accordance withthe present invention include hydrophilic monomers, such as acrylic acidor methacrylic acid, incorporated into the acrylic acid copolymers ofthe present invention along with one or more sulfonate-containingmonomers. The sulfonate anions of these monomers are softer thancarboxylate anions since the negative charge of the sulfonate anion isdelocalized over three oxygen atoms and a larger sulfur atom, as opposedto only two oxygen atoms and a smaller carbon atom in the carboxylateanion. These monomers, containing the softer sulfonate anion, are lessinteractive with multivalent ions present in hard water, particularlyCa²⁺ and Mg²⁺ ions. Suitable sulfonate-containing monomers include, butare not limited to, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS)and organic or inorganic salts of2-acrylamido-2-methyl-1-propanesulfonic acid, such as alkali earth metaland organic amine salts of 2-acrylamido-2-methyl-1-propanesulfonic acid,particularly the sodium salt of 2-acrylamido-2-methyl-1-propanesulfonicacid (NaAMPS). Additional suitable sulfonate-containing monomersinclude, but are not limited to, 2-methyl-2-propene sulfonic acid, vinylsulfonic acid, styrene sulfonic acid, 2-sulfopropyl methacrylate and3-sulfopropyl acrylate, and organic or inorganic salts thereof, such asalkali earth metals and organic amine salts, such as alkyl ammoniumhydroxide wherein the alkyl groups are C₁-C₁₈. To maintain thehydrophobic/hydrophilic balance of the ion-sensitive polymer, one ormore hydrophobic monomers are added to the polymer.

The ion-sensitive sulfonate anion modified acrylic acid copolymers ofthe present invention may be produced from monomers including thefollowing monomers: acrylic acid, methacrylic acid, or a combinationthereof; 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and organicor inorganic salts thereof, such as the sodium salt thereof (NaAMPS);butyl acrylate; and 2-ethylhexyl acrylate. Desirably, the ion-sensitivesulfonate anion modified acrylic acid copolymers of the presentinvention are produced from: acrylic acid; AMPS, NaAMPS or a combinationthereof; butyl acrylate; and 2-ethylhexyl acrylate. Desirably, themonomers are present in the sulfonate anion modified acrylic acidcopolymer at the following mole percents: acrylic acid, about 35 to lessthan 80 mole percent; AMPS or NaAMPS, greater than 0 to about 20 molepercent; butyl acrylate, from greater than 0 to about 65 mole percent;and 2-ethylhexyl acrylate, from greater than 0 to about 45 mole percent.More specifically, the monomers are present in the sulfonate anionmodified acrylic acid copolymer at the following mole percents: acrylicacid, about 50 to about 67 mole percent; AMPS or NaAMPS, from greaterthan 0 to about 10 mole percent; butyl acrylate, from about 15 to about28 mole percent; and 2-ethylhexyl acrylate, from about 7 to about 15mole percent. Most specifically, the monomers are present in thesulfonate anion modified acrylic acid copolymer at the following molepercents: acrylic acid, about 57 to about 66 mole percent; AMPS orNaAMPS, from about 1 to about 6 mole percent; butyl acrylate, from about15 to about 28 mole percent; and 2-ethylhexyl acrylate, from about 7 toabout 13 mole percent; especially, about 60 mole percent acrylic acid,about 5 mole percent AMPS or NaAMPS, about 24.5 mole percent butylacrylate and about 10.5 mole percent 2-ethylhexyl acrylate.

If AMPS is used as one of the monomers, it is desired to neutralize atleast a portion of the acid component. Any inorganic base or organicbase may be used as a neutralizing agent to neutralize the acidcomponent. Examples of neutralizing agents include, but are not limitedto, inorganic bases, such as sodium hydroxide, potassium hydroxide,lithium hydroxide and sodium carbonate, and amines, such asmonoethanolamine, diethanolamine, diethylaminoethanol, ammonia,trimethylamine, triethylamine, tripropylamine, morpholine. Preferredneutralizing agents include sodium hydroxide, potassium hydroxide, or acombination thereof.

A sulfonate modified copolymer having salt-sensitivity may also beproduced by sulfonation of an existing polymer, such as a copolymer oracrylic acid-derived terpolymer. Methods of sulfonating polymers arewell known in the art. Methods for the production of sulfonated orsulfated polymers are disclosed in U.S. Pat. No. 3,624,069, issued Nov.1971 to Schwelger; U.S. Pat. No. 4,419,403, issued Dec. 6, 1983 toVarona; U.S. Pat. No. 5,522,967, issued Jun. 4, 1996 to Shet; U.S. Pat.No. 4,220,739, issued Sep. 2, 1980 to Walles, U.S. Pat. No. 5,783,200,issued Jul. 21, 1998 to Motley et al., as well as the following patents:U.S. Pat. Nos. 2,400,720; 2,937,066; 2,786,780; 2,832,696; 3,613,957,and 3,740,258, all of which are herein incorporated by reference.Principles for sulfation and sulfonation (e.g., via sulfamic acidtreatment, reaction with thionyl chloride or chlorosulfonic acid, orexposure to sulfur trioxide) are among the pathways disclosed by SamuelShore and D. R. Berger in “Alcohol and Ether Alcohol Sulfates,” inAnionic Surfactants, Part 1, ed. Warner M. Linfield, New York: MarcelDekker, Inc., 1976, pp. 135-149; and by Ben E. Edwards, “The Mechanismsof Sulfonation and Sulfation,” in Anionic Surfactants, Part 1, ed.Warner M. Linfield, New York: Marcel Dekker, Inc., 1976, pp. 111-134,both of which are herein incorporated by reference.

In a further embodiment of the present invention, the above-describedion-sensitive polymer formulations are used as binder materials forflushable and/or non-flushable products. In order to be effective as abinder material in flushable products throughout the United States, theion-sensitive polymer formulations of the present invention remainstable and maintain their integrity while dry or in relatively lowconcentrations of monovalent ions, but become soluble in watercontaining up to about 200 ppm divalent ions, especially calcium andmagnesium ions. Desirably, the ion-sensitive polymer formulations of thepresent invention including acrylic acid copolymers are insoluble in asalt solution containing at least about 0.3 weight percent of one ormore inorganic and/or organic salts containing monovalent ions. Moredesirably, the ion-sensitive polymer formulations of the presentinvention including acrylic acid copolymers are insoluble in a saltsolution containing from about 0.3 weight percent to about 5.0 weightpercent of one or more inorganic and/or organic salts containingmonovalent ions. Even more desirably, the ion-sensitive polymerformulations of the present invention including acrylic acid copolymersare insoluble in salt solutions containing from about 1 weight percentto about 3.0 weight percent of one or more inorganic and/or organicsalts containing monovalent ions. Suitable monovalent ions include, butare not limited to, Na⁺ ions, K⁺ ions, Li⁺ ions, NH₄ ⁺ ions, lowmolecular weight quaternary ammonium compounds (e.g., those having fewerthan 5 carbons on any side group), and a combination thereof.

In an alternate embodiment, the ion-sensitive polymer formulations ofthe present invention including sulfonate anion modified acrylic acidcopolymers are insoluble in a salt solution containing at least about 1weight percent of one or more inorganic and/or organic salts containingmonovalent ions. More desirably, the ion-sensitive polymer formulationsof the present invention including sulfonate anion modified acrylic acidterpolymers are insoluble in a salt solution containing from about 1weight percent to about 5.0 weight percent of one or more inorganicand/or organic salts containing monovalent ions. Even more desirably,the ion-sensitive polymer formulations of the present inventionincluding sulfonate anion modified acrylic acid terpolymers areinsoluble in salt solutions containing from about 1 weight percent toabout 3.0 weight percent of one or more inorganic and/or organic saltscontaining monovalent ions. Suitable monovalent ions include, but arenot limited to, Na⁺ ions, K⁺ ions, Li⁺ ions, NH₄ ⁺ ions, low molecularweight quaternary ammonium compounds (e.g., those having fewer than 5carbons on any side group), and a combination thereof.

Based on a recent study conducted by the American Chemical Society,water hardness across the United States varies greatly, with CaCO₃concentration ranging from near zero for soft water to about 500 ppmCaCO₃ (about 200 ppm Ca²⁺ ion) for very hard water. To ensure polymerformulation dispersibility across the country (and throughout the wholeworld), the ion-sensitive polymer formulations of the present inventionare desirably soluble in water containing up to about 50 ppm Ca²⁺ and/orMg²⁺ ions. More desirably, the ion-sensitive polymer formulations of thepresent invention are soluble in water containing up to about 100 ppmCa²⁺ and/or Mg²⁺ ions. Even more desirably, the ion-sensitive polymerformulations of the present invention are soluble in water containing upto about 150 ppm Ca²⁺ and/or Mg²⁺ ions. Even more desirably, theion-sensitive polymer formulations of the present invention are solublein water containing up to about 200 ppm Ca²⁺ and/or Mg²⁺ ions.

A wide variety of polymer/surfactant systems may be used to provide thesame functionality as the ion-sensitive Lion polymers and theion-sensitive sulfonate anion modified acrylic acid terpolymers ofco-pending patent application Ser. No. 09/223,999, now U.S. Pat. No.6,423,884 without the need to be limited to sulfonic or carboxylicmoieties. Such other systems are described below.

Phosphorylated polymers containing phosphonic groups, thiophsulphonicgroups, or other organophosphorous groups as the “soft” anion capable ofestablishing a mismatch with Ca⁺⁺ may be used as the ion-sensitivepolymer in the present invention. This can include modified cellulose orcellulose derivatives and related gums, made insoluble by the presenceof monovalent salts or other electrolytes. In one embodiment, solublecellulose derivatives, such as CMC, are phosphorylated and renderedinsoluble and can be effective as ion-sensitive polymer formulationswhen in a solution of high ionic strength or of appropriate pH, but aredispersible in tap water. In another embodiment, aminophosphinic groupswhich can be anionic or amphoteric, are added to a polymer.Aminophosphinic groups can be added via condensation of a hypophosphitesalt with a primary amine. Reaction of chloromethylphosphinic acid withamines can also yield useful anionic groups, as described by Guenther W.Wasow in “Phosphorous-Containing Anionic Surfactants,” AnionicSurfactants: Organic Chemistry, ed. Helmut W. Stache, New York: MarcelDekker, 1996, pp. 589-590. The entire chapter by Wasow, comprising pages551-629 of the aforementioned book, offers additional teachings relevantto creating polymers with useful phosphorous groups, and is hereinincorporated by reference.

Other methods of preparing phosphorylated cellulose fibers are wellknown. These methods may be adapted to CMC, which may then serve as abinder agent. Exemplary methods are disclosed in U.S. Pat. No.3,739,782, issued Jun. 19, 1973 to Bernardin. Cellulose and synthetic ornatural polymers modified to have other “soft” anionic groups can beuseful as the ion-sensitive polymer of the present invention.

Natural polymers that are already provided with useful anionic groupsalso can be useful in the present invention. Such polymers include agarand carageenan, which have multiple ester sulfate groups. These may befurther modified, if necessary, to have additional anionic groups (e.g.,sulfonation, phosphorylation, and the like).

Polymers having two or more differing soft anionic groups, such as bothsulfonic and phosphonic groups, wherein the relative amounts of thediffering anions can be adjusted to optimize the strength, the ionicsensitivity, and the dispersibility of the polymer, are also useful inthe present invention. This also includes zwitterionic and amphotericcompounds. Polyampholytes in particular can be readily soluble above orbelow the isoelectric point, but insoluble at the isoelectric point,offering the potential for a triggering mechanism based on electrolyteconcentration and pH. Examples of polyampholytes include, but are notlimited to, copolymers of methacrylic acid and allylamine, copolymers ofmethacrylic acid and 2-vinylpyridine, polysiloxane ionomers with pendantamphoteric groups, and polymers formed directly from zwitterionicmonomeric salts, such as the ion-pair of co-monomers (IPC) of Salamoneet al., all as disclosed by Irja Piirma in Polymeric Surfactants, NewYork: Marcel Dekker, Inc., 1992, at pp. 251-254, incorporated herein byreference.

Proteins capable of being salted out, optionally modified to haveadditional soft ionic groups, can be useful as the ion-sensitive polymerof the present invention.

Systems such as those comprising algin derivatives or natural sulfonatedpolymers in which calcium ion in high concentrations (much higher thanthe levels of 250 ppm or less that may be encountered in hard water)insolubilize the binder, but allow even hard water to sufficientlydilute the calcium ion to render the binder dispersible are useful inthe present invention. Thus, while it is desired that the ion-sensitivebinders of the present invention be insoluble in solutions comprising amonovalent metal ion above a critical concentration, in some embodimentsuseful ion-sensitive binders are insoluble in solutions comprising adivalent metal ion above a critical concentration, but become solublewhen the divalent metal ion concentration falls to about 200 ppm or morespecifically to about 100 ppm, such that a fibrous substrate with theion-sensitive polymer as a binder maintains good wet strength in asolution comprising an elevated concentration of the divalent metal ion,yet becomes water dispersible in hard water or medium hard water. Thus,the triggering mechanism, which results in a pre-moistened wipe losingwet strength and becoming flushable even in hard water, can be due tothe dilution of a monovalent or divalent metal ion, and particularly analkali metal ion, with monovalent ions, such as sodium being preferred.Natural polymers and gums, which may be adapted for use as ion-sensitivebinders, are described by R. L. Whistler and J. N. BeMiller inIndustrial Gums, New York: Academic Press, Inc., 1973, incorporatedherein by reference. Natural polymers, which become firm or form a gelin the presence of calcium ions, are described below.

Algin (which may need to be in the form of sodium alginate and calciumalginate for good dispersibility, based on reported behavior in use abinder for medicinal tablets—see p. 62 of Whistler and BeMiller), whichis insoluble as alginic acid, calcium alginate, or in general as a saltof most polyvalent metals, but soluble as sodium alginate or as a saltwith low-molecular-weight amines or quaternary ammonium compounds (p.67) may be useful in the present invention. This material may be used,especially when zinc is an insolubilizing metal ion.

Other useful polymers include Carageenan and Iridophycan, both seaweedderivatives comprising ester sulfates.

Both natural polymers, including cellulose, and synthetic polymers canbe provided with anionic groups, such as sulfonic groups, phosphonicgroups, and carboxyl groups, capable of forming bridges to othermolecules in the presence of ions of a suitable type and concentration.When the ionic concentration is substantially changed, such as byplacing a cleansing article of the present invention in a toilet bowl,the article may become weak and disintegrate.

Ion-sensitive polymers include those which are dispersible in aqueousenvironment under prescribed conditions, yet are not dispersible in allaqueous environments. Examples include materials that are alkalinedispersible or saline insoluble. The Eastman AQ copolyesters (EastmanChemical Company, Kingsport, Tenn.), for example, can be dispersible indeionized water yet insoluble in saline solutions. They have beenproposed for use in articles such as diapers intended to absorb bodyfluids. Further information on those polymers is provided in EuropeanPatent Application 773,315-A1, “Nonwoven Web Comprising Water SolublePolyamides and Articles Constructed Therefrom,” published May 14, 1997by S. U. Ahmed.

Useful polyampholytes include polyacrylamide-based copolymers which arehighly sensitive to sodium chloride concentration.

U.S. Pat. No. 3,939,836, the disclosure of which is incorporated hereinby reference, describes an alkali salt of a sulfated cellulose esterresin which gives good dry tensile strength to fabrics, which strengthis retained in significant part when such fabrics are contacted with asalt solution typical of body fluids such as blood, menstrual fluid orurine and yet are readily dispersible in water. The resins have a degreeof sulfate substitution of from 0.10 to 0.45. In U.S. Pat. No.4,419,403, the disclosure of which is incorporated herein by reference,colloidal sulfate esters of cellulose are used for effectivewater-dispersible binders, wherein the binders have a much higher degreeof sulfate substitution than the '836 patent. The binders of the '403patent form gels in the presence of potassium ions. Other patentsrelated to dispersible polymers and wet wipes include U.S. Pat. Nos.4,117,187; 5,417,977; 4,309,469; 5,317,063; 5,312,883; 5,384,189;5,543,488; 5,571,876; 5,709,940; 5,718,790, the disclosures of which areincorporated herein by reference.

Co-binder Polymers

As stated above, the polymer formulations of the present invention areformed from a single ion-sensitive polymer or a combination of two ormore different polymers, wherein at least one polymer is anion-sensitive polymer. The second polymer may be a co-binder polymer. Aco-binder polymer is of a type and in an amount such that when combinedwith the ion-sensitive polymer, the co-binder polymer desirably islargely dispersed in the ion-sensitive polymer; i.e., the ion-sensitivepolymer is desirably the continuous phase and the co-binder polymer isdesirably the discontinuous phase. Desirably, the co-binder polymer canalso meet several additional criteria. For example, the co-binderpolymer can have a glass transition temperature; i.e., T_(g), that islower than the glass transition temperature of the ion-sensitivepolymer. Furthermore or alternatively, the co-binder polymer can beinsoluble in water, or can reduce the shear viscosity of theion-sensitive polymer. The co-binder can be present at a level relativeto the solids mass of the triggerable polymer of about 45% or less,specifically about 30% or less, more specifically about 20% or less,more specifically still about 15% or less, and most specifically about10% or less, with exemplary ranges of from about 1% to about 45% or fromabout 25% to about 35%, as well as from about 1% to about 20% or fromabout 5% to about 25%. The amount of co-binder present should be lowenough, for co-binders with the potential to form water insoluble bondsor films, that the co-binder remains a discontinuous phase unable tocreate enough crosslinked, or insoluble bonds, to jeopardize thedispersibility of the treated substrate. In one embodiment, theion-sensitive polymer formulation of the present invention can compriseabout 75 weight percent acrylic acid terpolymer and about 25 weightpercent poly(ethylene-vinyl acetate) co-binder.

Desirably, but not necessarily, the co-binder polymer when combined withthe ion-sensitive polymer will reduce the shear viscosity of theion-sensitive polymer to such an extent that the combination of theion-sensitive polymer and the co-binder polymer is sprayable. Bysprayable is mean that the polymer can be applied to a nonwoven fibroussubstrate by spraying and the distribution of the polymer across thesubstrate and the penetration of the polymer into the substrate are suchthat the polymer formulation is uniformly applied to the substrate.

The co-binder polymer can be in the form of an emulsion latex. Thesurfactant system used in such a latex emulsion should be such that itdoes not substantially interfere with the dispersibility of theion-sensitive polymer.

In some embodiments, the combination of the ion-sensitive polymer andthe co-binder polymer reduces the stiffness of the article to which itis applied compared to the article with just the ion-sensitive polymer.It has been found that when the ion-sensitive polymer, such as asulfonate anion modified acrylic acid terpolymer, is applied to anonwoven substrate, such as an air laid layer of wood pulp, for thepurpose of forming a wet wipe, the nonwoven sheet can have anundesirable amount of stiffness that is detrimental to the dry productfeel or to the handling of the dry web during processing, when thebrittleness of the dry substrate can harm runnability. By combining theion-sensitive polymer and the co-binder polymer, the stiffness of sucharticles can be reduced.

The co-binder polymer of the present invention can have an averagemolecular weight, which varies depending on the ultimate use of thepolymer. Desirably, the co-binder polymer has a weight average molecularweight ranging from about 500,000 to about 200,000,000. More desirably,the co-binder polymer has a weight average molecular weight ranging fromabout 500,000 to about 100,000,000.

Co-binder polymers that can meet many or all of the foregoing criteriainclude, but are not limited to, poly(ethylene-vinyl acetate),poly(styrene-butadiene), poly(styrene-acrylic), a vinyl acrylicterpolymer, neoprene, a polyester latex, an acrylic emulsion latex, polyvinyl chloride, ethylene-vinyl chloride copolymer, a carboxylated vinylacetate latex, and the like, all of which can be non-crosslinking (e.g.,devoid of N-methylol acrylamide or other crosslinkers), crosslinking, orpotentially crosslinking (i.e., prepared with a crosslinker present) butnot substantially crosslinked in the final product.

A particularly preferred non-crosslinking poly(ethylene-vinyl acetate)is Dur-O-Set® RB available from National Starch and Chemical Co.,Bridgewater, N.J. A particularly preferred non-crosslinkingpoly(styrene-butadiene) is Rovene® 4817 available from Mallard CreekPolymers, Charlotte, N.C. A particularly preferred non-crosslinkingpoly(styrene-acrylic) is Rhoplex® NM 1715K available from Rohm and Haas,Philadelphia, Pa.

When a latex co-binder, or any potentially crosslinkable co-binder isused, the latex should be prevented from forming substantialwater-insoluble bonds that bind the fibrous substrate together andinterfere with the dispersibility of the article. Thus, the latex can befree of crosslinking agents, such as NMA, or free of catalyst for thecrosslinker, or both. Alternatively, an inhibitor can be added thatinterferes with the crosslinker or with the catalyst such thatcrosslinking is impaired even when the article is heated to normalcrosslinking temperatures. Such inhibitors can include free radicalscavengers, methyl hydroquinone, t-butylcatechol, pH control agents suchas potassium hydroxide, and the like. For some latex crosslinkers, suchas N-methylol-acrylamide (NMA), for example, elevated pH such as a pH of8 or higher can interfere with crosslinking at normal crosslinkingtemperatures (e.g., about 130° C. or higher). Also alternatively, anarticle comprising a latex co-binder can be maintained at temperaturesbelow the temperature range at which crosslinking takes place, such thatthe presence of a crosslinker does not lead to crosslinking, or suchthat the degree of crosslinking remains sufficiently low that thedispersibility of the article is not jeopardized. Also alternatively,the amount of crosslinkable latex can be kept below a threshold levelsuch that even with crosslinking, the article remains dispersible. Forexample, a small quantity of crosslinkable latex dispersed as discreteparticles in an ion-sensitive binder can permit dispersibility even whenfully crosslinked. For the later embodiment, the amount of latex can bebelow about 20 weight percent, and, more specifically, below about 15weight percent relative to the ion-sensitive binder.

Latex compounds, whether crosslinkable or not, need not be theco-binder. SEM micrography of successful ion-sensitive binder films withuseful non-crosslinking latex emulsions dispersed therein has shown thatthe latex co-binder particles can remain as discrete entities in theion-sensitive binder, possibly serving in part as filler material. It isbelieved that other materials could serve a similar role, including adispersed mineral or particulate filler in the ion-sensitive binder,optionally comprising added surfactants/dispersants. For example, in oneenvisioned embodiment, freeflowing Ganzpearl PS-8F particles fromPresperse, Inc. (Piscataway, N.J.), a styrene/divinylbenzene copolymerwith about 0.4 micron particles, can be dispersed in an ion-sensitivebinder at a level of about 2 to 10 weight percent to modify themechanical, tactile, and optical properties of the ion-sensitive binder.Other filler-like approaches could include microparticles, microspheres,or microbeads of metal, glass, carbon, mineral, quartz, and/or plastic,such as acrylic or phenolic, and hollow particles having inert gaseousatmospheres sealed within their interiors. Examples include EXPANCELphenolic microspheres from Expancel of Sweden, which expandsubstantially when heated, or the acrylic microspheres known as PM 6545available from PQ Corporation of Pennsylvania. Foaming agents, includingCO₂ dissolved in the ion-sensitive binder, could also provide helpfuldiscontinuities as gas bubbles in the matrix of an ion-sensitive binder,allowing the dispersed gas phase in the ion-sensitive binder to serve asthe co-binder. In general, any compatible material that is not misciblewith the binder, especially one with adhesive or binding properties ofits own, can be used as the co-binder, if it is not provided in a statethat imparts substantial covalent bonds joining fibers in a way thatinterferes with the water-dispersibility of the product. However, thosematerials that also provide additional benefits, such as reduced sprayviscosity, can be especially preferred. Adhesive co-binders, such aslatex that do not contain crosslinkers or contain reduced amounts ofcrosslinkers, have been found to be especially helpful in providing goodresults over a wide range of processing conditions, including drying atelevated temperatures.

As stated above, the T_(g) of the co-binder polymer can be lower thanthe T_(g) of the ion-sensitive polymer, which is believed to improve theflexibility of the treated substrate, especially in the dry state. InTable 1 shown below is a comparison of the glass transition temperatureof some of the preferred polymers useful in the present invention.

TABLE 1 Glass Transition Temperatures For Select Polymers Polymer GlassTransition Temperature - Tg Sulfonate anion modified acrylic acid  55°C. terpolymer (dry) Sulfonate anion modified acrylic acid −22° C.terpolymer (wet) Rhoplex NW 1715K (dry)  −6° C. Rovene 4817 (dry)  −4°C. Elite 33 (dry)  10° C. Elite 22 (dry) −15° C.

In an alternate embodiment, the ion-sensitive polymer formulation of thepresent invention comprises about 55 to about 95 weight percentsulfonate anion modified acrylic acid terpolymer and about 5 to about 45weight percent poly(ethylene-vinyl acetate). More desirably, theion-sensitive polymer formulation of the present invention comprisesabout 75 weight percent sulfonate anion modified acrylic acid terpolymerand about 25 weight percent poly(ethylene-vinyl acetate).

As stated above, useful co-binder polymers can include a variety ofcommercial latex emulsions, including those selected from the Rovene®series (styrene butadiene latices available from Mallard Creek Polymersof Charlotte, N.C.), the Rhoplex® latices of Rohm and Haas Company, andthe Elite® latices of National Starch. Polymer emulsions or dispersionsgenerally comprise small polymer particles, such as crosslinkableethylene vinyl acetate copolymers, typically in spherical form,dispersed in water and stabilized with surface active ingredients suchas low molecular weight emulsifiers or high molecular weight protectivecolloids. These liquid binders can be applied to airlaid webs or othersubstrates by methods known in the art of binder treatment for nonwovenwebs, including spray or foam application, flooded nip impregnation,curtain coating, etc., followed by drying. In general, a wide variety oflatex compounds and other resins or emulsions can be considered,including vinyl acetate copolymer latices, such as 76 RES 7800 fromUnion Oil Chemicals Divisions and Resyn® 25-1103, Resyn® 25-1109, Resyn®25-1119, and Resyn® 25-1189 from National Starch and ChemicalCorporation, ethylene-vinyl acetate copolymer emulsions, such asAirflex® ethylene-vinylacetate from Air Products and Chemicals Inc.,acrylic-vinyl acetate copolymer emulsions, such as Rhoplex® AR-74 fromRohm and Haas Company, Synthemul® 97-726 from Reichhold Chemicals Inc.,Resyn® 25-1140, 25-1141, 25-1142, and Resyn-6820 from National Starchand Chemical Corporation, vinyl acrylic terpolymer latices, such as 76RES 3103 from Union Oil Chemical Division, and Resyn® 251110 fromNational Starch and Chemical Corporation, acrylic emulsion latices, suchas Rhoplex® B-15J, Rhoplex® P-376, Rhoplex® TR-407, Rhoplex® E-940,Rhoplex® TR934, Rhoplex® TR-520, Rhoplex® HA-24, and Rhoplex® NW1825from Rohm and Haas Company, and Hycar® 2600 X 322, Hycar® 2671, Hycar®2679, Hycar® 26120, and Hycar® 2600 X347 from B. F. Goodrich ChemicalGroup, styrene-butadiene latices, such as 76 RES 4100 and 76 RES 8100available from Union Oil Chemicals Division, Tylac® resin emulsion68-412, Tylac® resin emulsion 68-067, 68-319, 68-413, 68-500, 68-501,available from Reichhold Chemical Inc., and DL6672A, DL6663A, DL6638A,DL6626A, DL6620A, DL615A, DL617A, DL620A, DL640A, DL650A available fromDow Chemical Company; and rubber latices, such as neoprene availablefrom Serva Biochemicals; polyester latices, such as Eastman AQ 29Davailable from Eastman Chemical Company; vinyl chloride latices, such asGeon® 352 from B. F. Goodrich Chemical Group; ethylene-vinyl chloridecopolymer emulsions, such as Airflex® ethylene-vinyl chloride from AirProducts and Chemicals; polyvinyl acetate homopolymer emulsions, such asVinac® from Air Products and Chemicals; carboxylated vinyl acetateemulsion resins, such as Synthemul® synthetic resin emulsions 40-502,40-503, and 97-664 from Reichhold Chemicals Inc. and Polyco® 2149, 2150,and 2171 from Rohm and Haas Company. Silicone emulsions and binders canalso be considered.

The co-binder polymer can comprise surface active compounds that improvethe wettability of the substrate after application of the bindermixture.

Wettability of a dry substrate that has been treated with aion-sensitive polymer formulation can be a problem in some embodiments,because the hydrophobic portions of the ion-sensitive polymerformulation can become selectively oriented toward the air phase duringdrying, creating a hydrophobic surface that can be difficult to wet whenthe wetting composition is later applied unless surfactants are added tothe wetting composition. Surfactants, or other surface activeingredients, in co-binder polymers can improve the wettability of thedried substrate that has been treated with a ion-sensitive polymerformulation. Surfactants in the co-binder polymer should notsignificantly interfere with the ion-sensitive polymer formulation.Thus, the binder should maintain good integrity and tactile propertiesin the pre-moistened wipes with the surfactant present.

In one embodiment, an effective co-binder polymer replaces a portion ofthe ion-sensitive polymer formulation and permits a given strength levelto be achieved in a pre-moistened wipe with at least one of lowerstiffness, better tactile properties (e.g., lubricity or smoothness), orreduced cost, relative to an otherwise identical pre-moistened wipelacking the co-binder polymer and comprising the ion-sensitive polymerformulation at a level sufficient to achieve the given tensile strength.

Other Co-binder Polymers

The Dry Emulsion Powder (DEP) binders of Wacker Polymer Systems(Burghausen, Germany) such as the VINNEK® system of binders, can beapplied in some embodiments of the present invention. These areredispersible, free flowing binder powders formed from liquid emulsions.Small polymer particles from a dispersion are provided in a protectivematrix of water soluble protective colloids in the form of a powderparticle. The surface of the powder particle is protected against cakingby platelets of mineral crystals. As a result, polymer particles thatonce were in a liquid dispersion are now available in a free flowing,dry powder form that can be redispersed in water or turned into swollen,tacky particles by the addition of moisture. These particles can beapplied in highloft nonwovens by depositing them with the fibers duringthe airlaid process, and then later adding 10% to 30% moisture to causethe particles to swell and adhere to the fibers. This can be called the“chewing gum effect,” meaning that the dry, non-tacky fibers in the webbecome sticky like chewing gum once moistened. Good adhesion to polarsurfaces and other surfaces is obtained. These binders are available asfree flowing particles formed from latex emulsions that have been driedand treated with agents to prevent cohesion in the dry state. They canbe entrained in air and deposited with fibers during the airlaidprocess, or can be applied to a substrate by electrostatic means, bydirect contact, by gravity feed devices, and other means. They can beapplied apart from the binder, either before or after the binder hasbeen dried. Contact with moisture, either as liquid or steam, rehydratesthe latex particles and causes them to swell and to adhere to thefibers. Drying and heating to elevated temperatures (e.g., above 160°C.) causes the binder particles to become crosslinked and waterresistant, but drying at lower temperatures (e.g., at 110° C. or less)can result in film formation and a degree of fiber binding withoutseriously impairing the water dispersibility of the pre-moistened wipes.Thus, it is believed that the commercial product can be used withoutreducing the amount of crosslinker by controlling the curing of theco-binder polymer, such as limiting the time and temperature of dryingto provide a degree of bonding without significant crosslinking.

As pointed out by Dr. Klaus Kohlhammer in “New Airlaid Binders,”Nonwovens Report International, September 1999, issue 342, pp. 20-22,28-31, dry emulsion binder powders have the advantage that they caneasily be incorporated into a nonwoven or airlaid web during formationof the web, as opposed to applying the material to an existingsubstrate, permitting increased control over placement of the co-binderpolymer. Thus, a nonwoven or airlaid web can be prepared already havingdry emulsion binders therein, followed by moistening when theion-sensitive polymer formulation solution is applied, whereupon the dryemulsion powder becomes tacky and contributes to binding of thesubstrate. Alternatively, the dry emulsion powder can be entrapped inthe substrate by a filtration mechanism after the substrate has beentreated with ion-sensitive binder and dried, whereupon the dry emulsionpowder is rendered tacky upon application of the wetting composition.

In another embodiment, the dry emulsion powder is dispersed into theion-sensitive polymer formulation solution either by application of thepowder as the ion-sensitive polymer formulation solution is beingsprayed onto the web or by adding and dispersing the dry emulsion powderparticles into the ion-sensitive polymer formulation solution, afterwhich the mixture is applied to a web by spraying, by foam applicationmethods, or by other techniques known in the art.

Binder Formulations and Fabrics Containing the Same

The polymer formulations of the present invention may be used asbinders. The binder formulations of the present invention may be appliedto any fibrous substrate. The binders are particularly suitable for usein water-dispersible products. Suitable fibrous substrates include, butare not limited to, nonwoven and woven fabrics. In many embodiments,particularly personal care products, preferred substrates are nonwovenfabrics. As used herein, the term “nonwoven fabric” refers to a fabricthat has a structure of individual fibers or filaments randomly arrangedin a mat-like fashion (including papers). Nonwoven fabrics can be madefrom a variety of processes including, but not limited to, air-laidprocesses, wet-laid processes, hydroentangling processes, staple fibercarding and bonding, and solution spinning.

The binder composition may be applied to the fibrous substrate by anyknown process of application. Suitable processes for applying the bindermaterial include, but are not limited to, printing, spraying,electrostatic spraying, coating, flooded nips, metered press rolls,impregnating or by any other technique. The amount of binder compositionmay be metered and distributed uniformly within the fibrous substrate ormay be non-uniformly distributed within the fibrous substrate. Thebinder composition may be distributed throughout the entire fibroussubstrate or it may be distributed within a multiplicity of smallclosely spaced areas. In most embodiments, uniform distribution ofbinder composition is desired.

For ease of application to the fibrous substrate, the binder may bedissolved in water, or in a non-aqueous solvent such as methanol,ethanol, acetone, or the like, with water being the preferred solvent.The amount of binder dissolved in the solvent may vary depending on thepolymer used and the fabric application. Desirably, the binder solutioncontains up to about 25 percent by weight of binder composition solids.More desirably, the binder solution contains from about 10 to 20 percentby weight of binder composition solids, especially about 12 percent byweight binder composition solids. Plasticizers, perfumes, coloringagents, antifoams, bactericides, preservative, surface active agents,thickening agents, fillers, opacifiers, tackifiers, detackifiers, andsimilar additives can be incorporated into the solution of bindercomponents, if so desired.

Once the binder composition is applied to the substrate, the substrateis dried by any conventional means. Once dry, the coherent fibroussubstrate exhibits improved tensile strength when compared to thetensile strength of the untreated wet-laid or dry-laid substrates, andyet has the ability to rapidly “fall apart”, or disintegrate when placedin soft or hard water having a relatively high multivalent ionicconcentration and agitated. For example, the dry tensile strength of thefibrous substrate may be increased by at least 25 percent as compared tothe dry tensile strength of the untreated substrate not containing thebinder. More particularly, the dry tensile strength of the fibroussubstrate may be increase by at least 100 percent as compared to the drytensile strength of the untreated substrate not containing the binder.Even more particularly, the dry tensile strength of the fibroussubstrate may be increased by at least 500 percent as compared to thedry tensile strength of the untreated substrate not containing thebinder.

A desirable feature of the present invention is that the improvement intensile strength is effected where the amount of binder compositionpresent, “add-on”, in the resultant fibrous substrate represents only asmall portion by weight of the entire substrate. The amount of “add-on”can vary for a particular application; however, the optimum amount of“add-on” results in a fibrous substrate which has integrity while in useand also quickly disperses when agitated in water. For example, thebinder components typically are from about 5 to about 65 percent, byweight, of the total weight of the substrate. More particularly, thebinder components may be from about 10 to about 35 percent, by weight,of the total weight of the substrate. Even more particularly, the bindercomponents may be from about 17 to about 22 percent by weight of thetotal weight of the substrate.

The nonwoven fabrics of the present invention have good in-use tensilestrength, as well as, ion triggerability. Desirably, the nonwovenfabrics of the present invention are abrasion resistant and retainsignificant tensile strength in aqueous solutions containing greaterthan about 0.3 weight percent NaCl, or a mixture of monovalent ions, forthose formulations using the acrylic acid terpolymer, and greater thanabout 1 weight percent NaCl, or a mixture of monovalent ions, for thoseformulations using the sulfonate anion modified acrylic acid terpolymer.Yet, the nonwoven fabrics are dispersible in very soft to moderatelyhard to hard water. Because of this latter property, nonwoven fabrics ofthe present invention are well suited for disposable products, such assanitary napkins, diapers, adult incontinence products, and dry andpremoistened wipes (wet wipes), which can be thrown in a flush toiletafter use in any part of the world.

The fibers forming the fabrics above can be made from a variety ofmaterials including natural fibers, synthetic fibers, and combinationsthereof. The choice of fibers depends upon, for example, the intendedend use of the finished fabric and fiber cost. For instance, suitablefibrous substrates may include, but are not limited to, natural fiberssuch as cotton, linen, jute, hemp, wool, wood pulp, etc. Similarly,regenerated cellulosic fibers, such as viscose rayon and cuprammoniumrayon, modified cellulosic fibers, such as cellulose acetate, orsynthetic fibers, such as those derived from polypropylenes,polyethylenes, polyolefins, polyesters, polyamides, polyacrylics, etc.,alone or in combination with one another, may likewise be used. Blendsof one or more of the above fibers may also be used, if so desired.Among wood pulp fibers, any known papermaking fibers may be used,including softwood and hardwood fibers. Fibers, for example, may bechemically pulped or mechanically pulped, bleached or unbleached, virginor recycled, high yield or low yield, and the like. Mercerized,chemically stiffened or crosslinked fibers may also be used.

Synthetic cellulose fiber types include rayon in all its varieties andother fibers derived from viscose or chemically modified cellulose,including regenerated cellulose and solvent-spun cellulose, such asLyocell. Chemically treated natural cellulosic fibers can be used, suchas mercerized pulps, chemically stiffened or crosslinked fibers, orsulfonated fibers. Recycled fibers, as well as virgin fibers, can beused. Cellulose produced by microbes and other cellulosic derivativescan be used. As used herein, the term “cellulosic” is meant to includeany material having cellulose as a major constituent, and, specifically,comprising at least 50 percent by weight cellulose or a cellulosederivative. Thus, the term includes cotton, typical wood pulps,non-woody cellulosic fibers, cellulose acetate, cellulose triacetate,rayon, thermomechanical wood pulp, chemical wood pulp, debonded chemicalwood pulp, milkweed, or bacterial cellulose. The fiber length isimportant in producing the fabrics of the present invention. In someembodiments, such as flushable products, fiber length is of moreimportance. The minimum length of the fibers depends on the methodselected for forming the fibrous substrate. For example, where thefibrous substrate is formed by carding, the length of the fiber shouldusually be at least about 42 mm in order to insure uniformity.

Where the fibrous substrate is formed by air-laid or wet-laid processes,the fiber length may desirably be about 0.2 to 6 mm. Although fibershaving a length of greater than 50 mm are within the scope of thepresent invention, it has been determined that when a substantialquantity of fibers having a length greater than about 15 mm is placed ina flushable fabric, though the fibers will disperse and separate inwater, their length tends to form “ropes” of fibers, which areundesirable when flushing in home toilets. Therefore, for theseproducts, it is desired that the fiber length be about 15 mm or less sothat the fibers will not have a tendency to “rope” when they are flushedthrough a toilet. Although fibers of various lengths are applicable inthe present invention, desirably fibers are of a length less than about15 mm so that the fibers disperse easily from one another when incontact with water. The fibers, particularly synthetic fibers, can alsobe crimped

The fabrics of the present invention may be formed from a single layeror multiple layers. In the case of multiple layers, the layers aregenerally positioned in a juxtaposed or surface-to-surface relationshipand all or a portion of the layers may be bound to adjacent layers.Nonwoven webs of the present invention may also be formed from aplurality of separate nonwoven webs wherein the separate nonwoven websmay be formed from single or multiple layers. In those instances wherethe nonwoven web includes multiple layers, the entire thickness of thenonwoven web may be subjected to a binder application or each individuallayer may be separately subjected to a binder application and thencombined with other layers in a juxtaposed relationship to form thefinished nonwoven web.

In one embodiment, the fabric substrates of the present invention may beincorporated into cleansing and body fluid absorbent products, such assanitary napkins, diapers, adult incontinence products, surgicaldressings, tissues, wet wipes, and the like. These products may includean absorbent core, comprising one or more layers of an absorbent fibrousmaterial. The core may also comprise one or more layers of afluid-pervious element, such as fibrous tissue, gauze, plastic netting,etc. These are generally useful as wrapping materials to hold thecomponents of the core together. Additionally, the core may comprise afluid-impervious element or barrier means to preclude the passage offluid through the core and on the outer surfaces of the product.Desirably, the barrier means also is water-dispersible. A film of apolymer having substantially the same composition as the aforesaidwater-dispersible binder is particularly well-suited for this purpose.In accordance with the present invention, the polymer compositions areuseful for forming each of the above-mentioned product componentsincluding the layers of absorbent core, the fluid-pervious element, thewrapping materials, and the fluid-impervious element or barrier means.

The binder formulations of the present invention are particularly usefulfor binding fibers of air-laid nonwoven fabrics. These air-laidmaterials are useful for body-side liners, fluid distribution materials,fluid in-take materials, such as a surge material, absorbent wrap sheetand cover stock for various water-dispersible personal care products.Air-laid materials are particularly useful for use as a pre-moistenedwipe (wet wipe). The basis weights for air-laid non-woven fabrics mayrange from about 20 to about 200 grams per square meter (“gsm”) withstaple fibers having a denier of about 0.5-10 and a length of about 6-15millimeters. Surge, or in-take, materials need better resiliency andhigher loft so staple fibers having about 6 denier or greater are usedto make these products. A desirable final density for the surge, orin-take, materials is between about 0.025 grams per cubic centimeter(“g/cc”) to about 0.10 g/cc. Fluid distribution materials may have ahigher density, in the desired range of about 0.10 to about 0.20 g/ccusing fibers of lower denier, most desirable fibers have a denier ofless than about 1.5. Wipes generally can have a fiber density of about0.025 g/cc to about 0.2 g/cc and a basis weight of about 20 gsm to about150 gsm; specifically from about 30 to about 90 gsm, and mostspecifically from about 60 gsm to about 65 gsm.

The nonwoven fabrics of the present invention may also be incorporatedinto such body fluid absorbing products as sanitary napkins, diapers,surgical dressings, tissues and the like. In one embodiment, the binderis such that it will not dissolve when contacted by body fluids sincethe concentration of monovalent ions in the body fluids is above thelevel needed for dissolution; i.e., greater that 0.3% by weight and/orgreater than 1% by weight. The nonwoven fabric retains its structure,softness and exhibits a toughness satisfactory for practical use.However, when brought into contact with water having a concentration ofmultivalent ions, such as Ca²⁺ and Mg²⁺ ions, of up to about 200 ppm,the binder, such as one comprising a sulfonate anion modified acrylicacid terpolymer, disperses. Similarly, when brought into contact withwater having a concentration of multivalent ions, such as Ca²⁺ and Mg²⁺ions, of less than about 10 ppm, the binder comprising the acrylic acidterpolymer disperses. The nonwoven fabric structure is then easilybroken and dispersed in the water.

In one embodiment of the present invention, the in-use tensile strengthof a nonwoven fabric is enhanced by forming the nonwoven fabric with abinder material comprising an ion-sensitive polymer formulation of thepresent invention and subsequently applying one or more monovalentand/or multivalent salts to the nonwoven fabric. The salt may be appliedto the nonwoven fabric by any method known to those of ordinary skill inthe art including, but not limited to, applying a solid powder onto thefabric and spraying a salt solution onto the fabric. The amount of saltmay vary depending on a particular application. However, the amount ofsalt applied to the fabric is typically from about 0.1 weight percent toabout 10 weight percent salt solids based on the total weight of thefabric. The salt-containing fabrics of the present invention may be usedin a variety of fabric applications including, but not limited to,feminine pads, surgical dressings, and diapers.

Those skilled in the art will readily understand that the binderformulations and fibrous substrates of the present invention may beadvantageously employed in the preparation of a wide variety ofproducts, including but not limited to, absorbent personal care productsdesigned to be contacted with body fluids. Such products may onlycomprise a single layer of the fibrous substrate, or may comprise acombination of elements, as described above. Although the binderformulations and fibrous substrates of the present invention areparticularly suited for personal care products, the binder formulationsand fibrous substrates may be advantageously employed in a wide varietyof consumer products.

The combination of the acrylic acid terpolymer or the sulfonate anionmodified acrylic acid terpolymer and the non-crosslinkingpoly(ethylene-vinyl acetate) of the present invention produces improvedresults over the use of the terpolymer alone. For example, when theion-sensitive polymer formulation of the present invention is used for abinder composition for wet wipes, the wet wipes have improvedwettability on first insult without losing dispersibility which allowsthe wipe basesheet to wet out easily with the wet wipe solution atcommercial speeds. The ion-sensitive polymer formulation of the presentinvention also can reduce the stiffness of the dry basesheet, improvethe runnability of the dry and otherwise brittle sheet during furtherconversion of the product, reduce the stickiness of the wipes and/orimprove the sprayability of the ion-sensitive binder, thereby improvingbinder distribution and penetration in the basesheet.

Unlike other binder systems known in the art, the ion-sensitive polymerformulations of the present invention can be activated as binderswithout the need for elevated temperature. While drying or water removalis useful in achieving a good distribution of the binder in a fibrousweb, elevated temperature, per se, is not essential because the binderdoes not require crosslinking or other chemical reactions with highactivation energy to serve as a binder. Rather, the interaction with asoluble activating compound, typically a salt, is sufficient to causethe binder to become active (insoluble) or “salted out.” Thus, a dryingstep can be avoided, if desired, or replaced with low-temperature waterremoval operations such as room-temperature drying or freeze drying.Elevated temperature is generally helpful for drying, but the drying canbe done at temperatures below what is normally needed to drivecrosslinking reactions. Thus, the peak temperature to which thesubstrate is exposed or to which the substrate is brought can be belowany of the following: 180° C., 160° C., 140° C., 120° C., 110° C., 105°C., 100° C., 90° C., 75° C., and 60° C., with an exemplary range forpeak web temperature of from about 50° C. to about 110° C., or fromabout 70° C. to about 140° C. Of course, higher temperatures can beused, but are not necessary in most embodiments. While co-binder polymersystems, such as commercial latex emulsions, may also comprisecrosslinkers suited for reaction at temperatures of 160° C. or higher,maintaining a lower peak temperature can be beneficial in preventingdevelopment of excessive strength in the co-binder polymer that mightotherwise hinder the water dispersibility of the pre-moistened wipe.

Wet Wipe Wetting Composition and Wet Wipes Containing the Same

One particularly interesting embodiment of the present invention is theproduction of pre-moistened wipes, or wet wipes, from theabove-described ion-sensitive binder compositions and fibrous materials.For wipes, the fibrous material may be in the form of a woven ornonwoven fabric; however, nonwoven fabrics are more desirable. Thenonwoven fabric is, desirably, formed from relatively short fibers, suchas wood pulp fibers. The minimum length of the fibers depends on themethod selected for forming the nonwoven fabric. Where the nonwovenfabric is formed by a wet or dry method, the fiber length is desirablyfrom about 0.1 millimeters to 15 millimeters. Desirably, the nonwovenfabric of the present invention has a relatively low wet cohesivestrength when it is not bonded together by an adhesive or bindermaterial. When such nonwoven fabrics are bonded together by a bindercomposition, which loses its bonding strength in tap water and in sewerwater, the fabric will break up readily by the agitation provided byflushing and moving through the sewer pipes.

The finished wipes may be individually packaged, desirably in a foldedcondition, in a moisture proof envelope or packaged in containersholding any desired number of sheets in a water-tight package with awetting composition applied to the wipe. The finished wipes may also bepackaged as a roll of separable sheets in a moisture-proof containerholding any desired number of sheets on the roll with a wettingcomposition applied to the wipes. The roll can be coreless and eitherhollow or solid. Coreless rolls, including rolls with a hollow center orwithout a solid center, can be produced with known coreless rollwinders, including those of SRP Industry, Inc. (San Jose, Calif.);Shimizu Manufacturing (Japan), and the devices disclosed in U.S. Pat.No. 4,667,890, issued May 26, 1987 to Gietman. Solid-wound corelessrolls can offer more product for a given volume and can be adapted for awide variety of dispensers.

Relative to the weight of the dry fabric, the wipe may desirably containfrom about 10 percent to about 400 percent of the wetting composition,more desirably from about 100 percent to about 300 percent of thewetting composition, and even more desirably from about 180 percent toabout 240 percent of the wetting composition. The wipe maintains itsdesired characteristics over the time periods involved in warehousing,transportation, retail display and storage by the consumer. Accordingly,shelf life may range from two months to two years.

Various forms of impermeable envelopes and storage means for containingwet-packaged materials such as wipes and towelettes and the like arewell known in the art. Any of these may be employed in packaging thepre-moistened wipes of the present invention.

Desirably, the pre-moistened wipes of the present invention are wettedwith an aqueous wetting composition, which has one or more of thefollowing properties:

(1) is compatible with the above-described ion-sensitive bindercompositions of the present invention;

(2) enables the pre-moistened wipe to maintain its wet strength duringconverting, storage and usage (including dispensing), as well as,dispersibility in a toilet bowl;

(3) does not cause skin irritation;

(4) reduces tackiness of the wipe, and provides unique tactileproperties, such as skin glide and a “lotion-like feel”; and

(5) acts as a vehicle to deliver “moist cleansing” and other skin healthbenefits.

The wetting composition should not act as a solvent for the binder andgenerally does not contain solvents other than water, and particularlydoes not contain organic solvents, though a small quantity (<1%) of afragrance solubilizer such as polysorbate 20 may be present, dependingon the fragrance and the salt concentration of the wetting composition.Desirably, the wetting composition contains less than about 10 weightpercent of organic solvents, such as propylene glycol or other glycols,polyhydroxy alcohols, and the like, based on the total weight of thewetting composition. More desirably, the wetting composition containsless than about 4 weight percent of organic solvents. Even moredesirably, the wetting composition contains less than about 1 weightpercent of organic solvents. The wetting composition can besubstantially free of organic solvents.

One aspect of the present invention is a wetting composition, whichcontains an activating compound that maintains the strength of awater-dispersible binder until the activating compound is diluted withwater, whereupon the strength of the water-dispersible binder begins todecay. The water-dispersible binder may be any of the ion-sensitivebinder compositions of the present invention or any other ion-sensitivebinder composition. The activating compound in the wetting compositioncan be a salt, such as sodium chloride, or any other compound, whichprovides in-use and storage strength to the water-dispersible bindercomposition, and can be diluted in water to permit dispersion of thesubstrate as the binder polymer triggers to a weaker state. Desirably,the wetting composition contains less than about 10 weight percent of anactivating compound based on the total weight of the wettingcomposition. Specifically, the wetting composition may contain fromabout 0.3 weight percent to about 5 weight percent of an activatingcompound. Even more specifically, the wetting composition may containfrom about 2 weight percent to about 4 weight percent of an activatingcompound.

The wetting composition of the present invention may further comprise avariety of additives compatible with the activating compound and thewater-dispersible binder, such that the strength and dispersibilityfunctions of the wipe are not jeopardized. Suitable additives in thewetting composition include, but are not limited to, the followingadditives: skin-care additives; odor control agents; detackifying agentsto reduce the tackiness of the binder; particulates; antimicrobialagents; preservatives; wetting agents and cleaning agents such asdetergents, surfactants, and some silicones; emollients; surface feelmodifiers for improved tactile sensation (e.g., lubricity) on the skin;fragrance; fragrance solubilizers; opacifiers; fluorescent whiteningagents; UV absorbers; pharmaceuticals; and pH control agents, such asmalic acid or potassium hydroxide.

Skin-Care Additives

As used herein, the term “skin-care additives” represents additives,which provide one or more benefits to the user, such as a reduction inthe probability of having diaper rash and/or other skin damage caused byfecal enzymes. These enzymes, particularly trypsin, chymotrypsin andelastase, are proteolytic enzymes produced in the gastrointestinal tractto digest food. In infants, for example, the feces tend to be watery andcontain, among other materials, bacteria, and some amounts of undegradeddigestive enzymes. These enzymes, if they remain in contact with theskin for any appreciable period of time, have been found to cause anirritation that is uncomfortable in itself and can predispose the skinto infection by microorganisms. As a countermeasure, skin-care additivesinclude, but are not limited to, the enzyme inhibitors and sequestrantsset forth hereafter. The wetting composition may contain less than about5 weight percent of skin-care additives based on the total weight of thewetting composition. More specifically, the wetting composition maycontain from about 0.01 weight percent to about 2 weight percent ofskin-care additives. Even more specifically, the wetting composition maycontain from about 0.01 weight percent to about 0.05 weight percent ofskin-care additives.

A variety of skin-care additives may be added to the wetting compositionand the pre-moistened wipes of the present invention or includedtherein. In one embodiment of the present invention, skin-care additivesin the form of particles are added to serve as fecal enzyme inhibitors,offering potential benefits in the reduction of diaper rash and skindamage caused by fecal enzymes. U.S. Pat. No. 6,051,749, issued Apr. 18,2000 to Schulz et al., the entirety of which is herein incorporated byreference, discloses organophilic clays in a woven or nonwoven web, saidto be useful for inhibiting fecal enzymes. Such materials may be used inthe present invention, including reaction products of a long chainorganic quaternary ammonium compound with one or more of the followingclays: montmorillonite, bentonite, beidellite, hectorite, saponite, andstevensite.

Other known enzyme inhibitors and sequestrants may be used as skin-careadditives in the wetting composition of the present invention, includingthose that inhibit trypsin and other digestive or fecal enzymes, andinhibitors for urease. For example, enzyme inhibitors and anti-microbialagents may be used to prevent the formation of odors in body fluids. Forexample, urease inhibitors, which are also said to play a role in odorabsorption, are disclosed by T. Trinh in World Patent Application No.98/26808, “Absorbent Articles with Odor Control System,” published Jun.25, 1998, the entirety of which is herein incorporated by reference.Such inhibitors may be incorporated into the wetting composition and thepre-moistened wipes of the present invention and include transitionmetal ions and their soluble salts, such as silver, copper, zinc,ferric, and aluminum salts. The anion may also provide ureaseinhibition, such as borate, phytate, etc. Compounds of potential valueinclude, but are not limited to, silver chlorate, silver nitrate,mercury acetate, mercury chloride, mercury nitrate, copper metaborate,copper bromate, copper bromide, copper chloride, copper dichromate,copper nitrate, copper salicylate, copper sulfate, zinc acetate, zincborate, zinc phytate, zinc bromate, zinc bromide, zinc chlorate, zincchloride, zinc sulfate, cadmium acetate, cadmium borate, cadmiumbromide, cadmium chlorate, cadmium chloride, cadmium formate, cadmiumiodate, cadmium iodide, cadmium permanganate, cadmium nitrate, cadmiumsulfate, and gold chloride.

Other salts that have been disclosed as having urease inhibitionproperties include ferric and aluminum salts, especially the nitrates,and bismuth salts. Other urease inhibitors are disclosed by Trinh,including hydroxamic acid and its derivatives; thiourea; hydroxylamine;salts of phytic acid; extracts of plants of various species, includingvarious tannins, e.g. carob tannin, and their derivatives such aschlorogenic acid derivatives; naturally occurring acids such as ascorbicacid, citric acid, and their salts; phenyl phosphoro diamidate/diaminophosphoric acid phenyl ester; metal aryl phosphoramidate complexes,including substituted phosphorodiamidate compounds; phosphoramidateswithout substitution on the nitrogen; boric acid and/or its salts,including especially, borax, and/or organic boron acid compounds; thecompounds disclosed in European Patent Application 408,199; sodium,copper, manganese, and/or zinc dithiocarbamate; quinones; phenols;thiurams; substituted rhodanine acetic acids; alkylated benzoquinones;formamidine disulphide; 1:3-diketones maleic anhydride; succinamide;phthalic anhydride; pehenic acid; /N,N-dihalo-2-imidazolidinones;N-halo2-oxazolidinones; thio- and/or acylphosphoryltnamide and/orsubstituted derivatives thereof-, thiopyridine-N-oxides, thiopyridines,and thiopyrimidines; oxidized sulfur derivatives of diaminophosphinylcompounds; cyclotriphosphazatriene derivatives; orthodiaminophosphinylderivatives of oximes; bromo-nitro compounds; S-aryl and/or alkyldiamidophosphorothiolates; diaminophosphinyl derivatives; mono- and/orpolyphosphorodiamide; 5-substituted-benzoxathiol-2-ones;N(diaminophosphinyl)arylcarboxamides; alkoxy-1,2-benzothaizin compounds;etc.

Many other skin-care additives may be incorporated into the wettingcomposition and pre-moistened wipes of the present invention, including,but not limited to, sun blocking agents and UV absorbers, acnetreatments, pharmaceuticals, baking soda (including encapsulated formsthereof), vitamins and their derivatives such as Vitamins A or E,botanicals such as witch hazel extract and aloe vera, allantoin,emollients, disinfectants, hydroxy acids for wrinkle control oranti-aging effects, sunscreens, tanning promoters, skin lighteners,deodorants and antiperspirants, ceramides for skin benefits and otheruses, astringents, moisturizers, nail polish removers, insectrepellants, antioxidants, antiseptics, anti-inflammatory agents and thelike, provided that the additives are compatible with an ion-sensitivebinder composition associated therewith, and especially theion-sensitive binder compositions of the present invention (i.e., theydo not cause a substantial loss of strength in the wet state of thepre-moistened wipes, prior to dilution in water, while permittingdispersibility in water).

Useful materials for skin care and other benefits are listed inMcCutcheon's 1999, Vol. 2: Functional Materials, MC Publishing Company,Glen Rock, N.J. Many useful botanicals for skin care are provided byActive Organics, Lewisville, Tex.

Odor Control Additives

Suitable odor control additives for use in the wetting composition andpre-moistened wipes of the present invention include, but are notlimited to, zinc salts; talc powder; encapsulated perfumes (includingmicrocapsules, macrocapsules, and perfume encapsulated in liposomes,vessicles, or microemulsions); chelants, such as ethylenediaminetetra-acetic acid; zeolites; activated silica, activated carbon granulesor fibers; activated silica particulates; polycarboxylic acids, such ascitric acid; cyclodextrins and cyclodextrin derivatives; chitosan orchitin and derivatives thereof; oxidizing agents; antimicrobial agents,including silver-loaded zeolites (e.g., those of BF Technologies,located in Beverly, Mass., sold under the trademark HEALTHSHIELD™);triclosan; kieselguhr; and mixtures thereof. In addition to controllingodor from the body or body wastes, odor control strategies can also beemployed to mask or control any odor of the treated substrate.Desirably, the wetting composition contains less than about 5 weightpercent of odor control additives based on the total weight of thewetting composition. More desirably, the wetting composition containsfrom about 0.01 weight percent to about 2 weight percent of odor controladditives. Even more desirably, the wetting composition contains fromabout 0.03 weight percent to about 1 weight percent of odor controladditives.

In one embodiment of the present invention, the wetting compositionand/or pre-moistened wipes comprise derivatized cyclodextrins, such ashydroxypropyl beta-cyclodextrin in solution, which remain on the skinafter wiping and provide an odor-absorbing layer. In other embodiments,the odor source is removed or neutralized by application of anodor-control additive, exemplified by the action of a chelant that bindsmetal groups necessary for the function of many proteases and otherenzymes that commonly produce an odor. Chelating the metal groupinterferes with the enzyme's action and decreases the risk of malodor inthe product.

Principles for the application of chitosan or chitin derivatives tononwoven webs and cellulosic fibers are described by S. Lee et al. in“Antimicrobial and Blood Repellent Finishes for Cotton and NonwovenFabrics Based on Chitosan and Fluoropolymers,” Textile Research Journal,69(2); 104-112, February 1999.

Detackifying Agents

While elevated salt concentrations may reduce the tack of theion-sensitive binder, other means of tack reduction are often desirable.Thus, detackifying agents may be used in the wetting composition toreduce the tackiness, if any, of the ion-sensitive binder. Suitabledetackifiers include any substance known in the art to reduce tackbetween two adjacent fibrous sheets treated with an adhesive-likepolymer or any substance capable of reducing the tacky feel of anadhesive-like polymer on the skin. Detackifiers may be applied as solidparticles in dry form, as a suspension or as a slurry of particles.Deposition may be by spray, coating, electrostatic deposition,impingement, filtration (i.e., a pressure differential drives aparticle-laden gas phase through the substrate, depositing particles bya filtration mechanism), and the like, and may be applied uniformly onone or more surfaces of the substrate or may be applied in a pattern(e.g., repeating or random patterns) over a portion of the surface orsurfaces of the substrate. The detackifier may be present throughout thethickness of the substrate, but may be concentrated at one or bothsurfaces, and may be substantially only present on one or both surfacesof the substrate.

Specific detackifiers include, but are not limited to, powders, such astalc powder, calcium carbonate, mica; starches, such as corn starch;lycopodium powder; mineral fillers, such as titanium dioxide; silicapowder; alumina; metal oxides in general; baking powder; kieselguhr; andthe like. Polymers and other additives having low surface energy mayalso be used, including a wide variety of fluorinated polymers, siliconeadditives, polyolefins and thermoplastics, waxes, debonding agents knownin the paper industry including compounds having alkyl side chains suchas those having 16 or more carbons, and the like. Compounds used asrelease agents for molds and candle making may also be considered, aswell as, dry lubricants and fluorinated release agents.

In one embodiment, the detackifier comprises polytetrafluorethylene(PTFE), such as PTFE telomer (KRYTOX® DF) compound, used in the PTFErelease agent dry lubricant MS-122DF, marketed by Miller-Stephenson(Danbury, Conn.) as a spray product. For example, PTFE particles may beapplied by spray to one side of the substrate prior to winding of thepre-moistened wipes. In one embodiment, a detackifying agent is appliedto only one surface of the substrate prior to winding into a roll.

The wetting composition desirably contains less than about 25 weightpercent of detackifying agents based on the total weight of the wettingcomposition. More desirably, the wetting composition contains from about0.01 weight percent to about 10 weight percent of detackifying agents,more specifically about 5% or less. Even more specifically, the wettingcomposition contains from about 0.05 weight percent to about 2 weightpercent of detackifying agents.

In addition to acting as a detackifying agent, starch compounds may alsoimprove the strength properties of the pre-moistened wipes. For example,it has been found that ungelled starch particles, such as hydrophilictapioca starch, when present at a level of about 1% or higher by weightrelative to the weight of the wetting composition, can permit thepre-moistened wipe to maintain the same strength at a lower saltconcentration than is possible without the presence of starch. Thus, forexample, a given strength can be achieved with 2% salt in the wettingcomposition in the presence of salt compared to a level of 4% salt beingneeded without starch. Starch may be applied by adding the starch to asuspension of laponite to improve the dispersion of the starch withinthe wetting composition.

Microparticulates

The wetting composition of the present invention may be further modifiedby the addition of solid particulates or microparticulates. Suitableparticulates include, but are not limited to, mica, silica, alumina,calcium carbonate, kaolin, talc, and zeolites. The particulates may betreated with stearic acid or other additives to enhance the attractionor bridging of the particulates to the binder system, if desired. Also,two-component microparticulate systems, commonly used as retention aidsin the papermaking industry, may also be used. Such two-componentmicroparticulate systems generally comprise a colloidal particle phase,such as silica particles, and a water-soluble cationic polymer forbridging the particles to the fibers of the web to be formed. Thepresence of particulates in the wetting composition can serve one ormore useful functions, such as (1) increasing the opacity of thepre-moistened wipes; (2) modifying the rheology or reducing thetackiness of the pre-moistened wipe; (3) improving the tactileproper-ties of the wipe; or (4) delivering desired agents to the skinvia a particulate carrier, such as a porous carrier or a microcapsule.Desirably, the wetting composition contains less than about 25 weightpercent of particulate based on the total weight of the wettingcomposition. More specifically, the wetting composition may contain fromabout 0.05 weight percent to about 10 weight percent ofmicroparticulate. Even more specifically, the wetting composition maycontain from about 0.1 weight percent to about 5 weight percent ofmicroparticulate.

Microcapsules and Other Delivery Vehicles

Microcapsules and other delivery vehicles may also be used in thewetting composition of the present invention to provide skin-careagents; medications; comfort promoting agents, such as eucalyptus;perfumes; skin care agents; odor control additives; vitamins; powders;and other additives to the skin of the user. Specifically, the wettingcomposition may contain up to about 25 weight percent of microcapsulesor other delivery vehicles based on the total weight of the wettingcomposition. More specifically, the wetting composition may contain fromabout 0.05 weight percent to about 10 weight percent of microcapsules orother delivery vehicles. Even more specifically, the wetting compositionmay contain from about 0.2 weight percent to about 5.0 weight per centof microcapsules or other delivery vehicles.

Microcapsules and other delivery vehicles are well known in the art. Forexample, POLY-PORE® E200 (Chemdal Corp., Arlington Heights, Ill.), is adelivery agent comprising soft, hollow spheres that can contain anadditive at over 10 times the weight of the delivery vehicle. Knownadditives reported to have been used with POLY-PORE® E200 include, butare not limited to, benzoyl peroxide, salicylic acid, retinol, retinylpalmitate, octyl methoxycinnamate, tocopherol, silicone compounds (DC435), and mineral oil. Another useful delivery vehicle is a sponge-likematerial marketed as POLY-PORE® L200, which is reported to have beenused with silicone (DC 435) and mineral oil. Other known deliverysystems include cyclodextrins and their derivatives, liposomes,polymeric sponges, and spray-dried starch.

Additives present in microcapsules are isolated from the environment andthe other agents in the wetting composition until the wipe is applied tothe skin, whereupon the microcapsules break and deliver their load tothe skin or other surfaces.

Preservatives and Anti-Microbial Agents

The wetting composition of the present invention may also containpreservatives and/or anti-microbial agents. Several preservatives and/oranti-microbial agents, such as Mackstat H 66 (available from McIntyreGroup, Chicago, Ill.), have been found to give excellent results inpreventing bacteria and mold growth. Other suitable preservatives andanti-microbial agents include, but are not limited to DMDM hydantoin(e.g., Glydant Plus™, Lonza, Inc., Fair Lawn, N.J.), iodopropynylbutylcarbamate, Kathon (Rohm and Hass, Philadelphia, Pa.),methylparaben, propylparaben, 2-bromo-2-nitropropane-1,3-diol, benzoicacid, and the like. Desirably, the wetting composition contains lessthan about 2 weight percent on an active basis of preservatives and/oranti-microbial agents based on the total weight of the wettingcomposition. More desirably, the wetting composition contains from about0.01 weight percent to about 1 weight percent of preservatives and/oranti-microbial agents. Even more desirably, the wetting compositioncontains from about 0.01 weight percent to about 0.5 weight percent ofpreservatives and/or anti-microbial agents.

Wetting Agents and Cleaning Agents

A variety of wetting agents and/or cleaning agents may be used in thewetting composition of the present invention. Suitable wetting agentsand/or cleaning agents include, but are not limited to, detergents andnonionic, amphoteric, and anionic surfactants, especially aminoacid-based surfactants. Amino acid-based surfactant systems, such asthose derived from amino acids L-glutamic acid and other natural fattyacids, offer pH compatibility to human skin and good cleansing power,while being relatively safe and providing improved tactile andmoisturization properties compared to other anionic surfactants. Onefunction of the surfactant is to improve wetting of the dry substratewith the wetting composition. Another function of the surfactant can beto disperse bathroom soils when the pre-moistened wipe contacts a soiledarea and to enhance their absorption into the substrate. The surfactantcan further assist in make-up removal, general personal cleansing, hardsurface cleansing, odor control, and the like.

One commercial example of an amino-acid based surfactant isacylglutamate, marketed under the Amisoft name by Ajinomoto Corp.,Tokyo, Japan. Desirably, the wetting composition contains less thanabout 3 weight percent of wetting agents and/or cleaning agents based onthe total weight of the wetting composition. More desirably, the wettingcomposition contains from about 0.01 weight percent to about 2 weightpercent of wetting agents and/or cleaning agents. Even more desirably,the wetting composition contains from about 0.1 weight percent to about0.5 weight percent of wetting agents and/or cleaning agents.

Although amino-acid based surfactant are particularly useful in thewetting compositions of the present invention, a wide variety ofsurfactants may be used in the present invention. Suitable non-ionicsurfactants include, but are not limited to, the condensation productsof ethylene oxide with a hydrophobic (oleophilic)polyoxyalkylene baseformed by the condensation of propylene oxide with propylene glycol. Thehydrophobic portion of these compounds desirably has a molecular weightsufficiently high so as to render it water-insoluble. The addition ofpolyoxyethylene moieties to this hydrophobic portion increases thewater-solubility of the molecule as a whole, and the liquid character ofthe product is retained up to the point where the polyoxyethylenecontent is about 50% of the total weight of the condensation product.Examples of compounds of this type include commercially-availablePluronic surfactants (BASF Wyandotte Corp.), especially those in whichthe polyoxypropylene ether has a molecular weight of about 1500-3000 andthe polyoxyethylene content is about 35-55% of the molecule by weight,i.e. Pluronic L-62.

Other useful nonionic surfactants include, but are not limited to, thecondensation products of C₈-C₂₂ alkyl alcohols with 2-50 moles ofethylene oxide per mole of alcohol. Examples of compounds of this typeinclude the condensation products of C₁₁-C₁₅ secondary alkyl alcoholswith 3-50 moles of ethylene oxide per mole of alcohol, which arecommercially-available as the Poly-Tergent SLF series from OlinChemicals or the TERGITOL® series from Union Carbide, i.e. TERGITOL®25-L-7, which is formed by condensing about 7 moles of ethylene oxidewith a C₁₂-C₁₅ alkanol.

Other nonionic surfactants, which may be employed in the wettingcomposition of the present invention, include the ethylene oxide estersof C₆-C₁₂ alkyl phenols such as (nonylphenoxy)polyoxyethylene ether.Particularly useful are the esters prepared by condensing about 8-12moles of ethylene oxide with nonylphenol, i.e. the IGEPAL® CO series(GAF Corp.).

Further non-ionic surface active agents include, but are not limited to,alkyl polyglycosides (APG), derived as a condensation product ofdextrose (D-glucose) and a straight or branched chain alcohol. Theglycoside portion of the surfactant provides a hydrophile having highhydroxyl density, which enhances water solubility. Additionally, theinherent stability of the acetal linkage of the glycoside provideschemical stability in alkaline systems. Furthermore, unlike somenon-ionic surface active agents, alkyl polyglycosides have no cloudpoint, allowing one to formulate without a hydrotrope, and these arevery mild, as well as readily biodegradable non-ionic surfactants. Thisclass of surfactants is available from Horizon Chemical under the tradenames of APG-300, APG-350, APG-500, and APG-500.

Silicones are another class of wetting agents available in pure form, oras microemulsions, macroemulsions, and the like. One exemplary non-ionicsurfactant group is the silicone-glycol copolymers. These surfactantsare prepared by adding poly(lower)alkylenoxy chains to the free hydroxylgroups of dimethylpolysiloxanols and are available from the Dow CorningCorp as Dow Corning 190 and 193 surfactants (CTFA name: dimethiconecopolyol). These surfactants function, with or without any volatilesilicones used as solvents, to control foaming produced by the othersurfactants, and also impart a shine to metallic, ceramic, and glasssurfaces.

Anionic surfactants may also be used in the wetting compositions of thepresent invention. Anionic surfactants are useful due to their highdetergency include anionic detergent salts having alkyl substituents of8 to 22 carbon atoms such as the water-soluble higher fatty acid alkalimetal soaps, e.g., sodium myristate and sodium palmitate. A preferredclass of anionic surfactants encompasses the water-soluble sulfated andsulfonated anionic alkali metal and alkaline earth metal detergent saltscontaining a hydrophobic higher alkyl moiety (typically containing fromabout 8 to 22 carbon atoms) such as salts of higher alkyl mono orpolynuclear aryl sulfonates having from about 1 to 16 carbon atoms inthe alkyl group, with examples available as the Bio-Soft series, i.e.Bio-Soft D-40 (Stepan Chemical Co.).

Other useful classes of anionic surfactants include, but are not limitedto, the alkali metal salts of alkyl naphthalene sulfonic acids (methylnaphthalene sodium sulfonate, Petro AA, Petrochemical Corporation);sulfated higher fatty acid monoglycerides such as the sodium salt of thesulfated monoglyceride of cocoa oil fatty acids and the potassium saltof the sulfated monoglyceride of tallow fatty acids; alkali metal saltsof sulfated fatty alcohols containing from about 10 to 18 carbon atoms(e.g., sodium lauryl sulfate and sodium stearyl sulfate); sodiumC₁₄-C₁₆-alphaolefin sulfonates such as the Bio-Terge series (StepanChemical Co.); alkali metal salts of sulfated ethyleneoxy fatty alcohols(the sodium or ammonium sulfates of the condensation products of about 3moles of ethylene oxide with a C₁₂-C₁₅ n-alkanol, i.e., the Neodolethoxysulfates, Shell Chemical Co.); alkali metal salts of higher fattyesters of low molecular weight alkylol sulfonic acids, e.g. fatty acidesters of the sodium salt of isothionic acid, the fatty ethanolamidesulfates; the fatty acid amides of amino alkyl sulfonic acids, e.g.lauric acid amide of taurine; as well as numerous other anionic organicsurface active agents such as sodium xylene sulfonate, sodiumnaphthalene sulfonate, sodium toulene sulfonate and mixtures thereof.

A further useful class of anionic surfactants includes the8-(4-n-alkyl-2-cyclohexenyl)-octanoic acids, wherein the cyclohexenylring is substituted with an additional carboxylic acid group. Thesecompounds or their potassium salts, are commercially-available fromWestvaco Corporation as Diacid 1550 or H-240. In general, these anionicsurface active agents can be employed in the form of their alkali metalsalts, ammonium or alkaline earth metal salts.

Macroemulsions and Microemulsion of Silicone Particles

The wetting composition may further comprise an aqueous microemulsion ofsilicone particles. For example, U.S. Pat. No. 6,037,407, “Process forthe Preparation of Aqueous Emulsions of Silicone Oils and/or Gums and/orResins” issued Mar. 14, 2000, discloses organopolysiloxanes in anaqueous microemulsion. Desirably, the wetting composition contains lessthan about 5 weight percent of a microemulsion of silicone particlesbased on the total weight of the wetting composition. More desirably,the wetting composition contains from about 0.02 weight percent to about3 weight percent of a microemulsion of silicone particles. Even moredesirably, the wetting composition contains from about 0.02 weightpercent to about 0.5 weight percent of a microemulsion of siliconeparticles.

Silicone emulsions in general may be applied to the pre-moistened wipeby any known coating method. For example, the pre-moistened wipe may bemoistened with an aqueous composition comprising a water-dispersible orwater-miscible, silicone-based component that is compatible with theactivating compound in the wetting composition. Further, the wipe cancomprise a nonwoven web of fibers having a water-dispersible binder,wherein the web is moistened with a lotion comprising a silicone-basedsulfosuccinate. The silicone-based sulfosuccinate provides gentle andeffective cleansing without a high level of surfactant. Additionally,the silicone-based sulfosuccinate provides a solubilization function,which prevents precipitation of oil-soluble components, such asfragrance components, vitamin extracts, plant extracts, and essentialoils.

In one embodiment of the present invention, the wetting compositioncomprises a silicone copolyol sulfosuccinate, such as disodiumdimethicone copolyol sulfosuccinate and diammonium dimethiconecopolyolsulfosuccinate. Desirably, the wetting composition comprisesless than about 2 percent by weight of the silicone-basedsulfosuccinate, and more desirably from about 0.05 percent to about 0.30percent by weight of the silicone-based sulfosuccinate.

In another example of a product comprising a silicone emulsions, DowCorning 9506 powder may also be present in the wetting composition. DowCorning 9506 powder is believed to comprise adimethicone/vinyldimethicone cross-polymer and is a spherical powder,which is said to be useful in controlling skin oils (see “New ChemicalPerspectives,” Soap and Cosmetics, Vol. 76, No. 3, March 2000, p. 12).Thus, a water-dispersible wipe, which delivers a powder effective incontrolling skin oil, is also within the scope of the present invention.Principles for preparing silicone emulsions are disclosed in WO97/10100, published Mar. 20, 1997.

Emollients

The wetting composition of the present invention may also contain one ormore emollients. Suitable emollients include, but are not limited to,PEG 75 lanolin, methyl gluceth 20 benzoate, C₁₂-C₁₅ alkyl benzoate,ethoxylated cetyl stearyl alcohol, products marketed as Lambent waxWS-L, Lambent WD-F, Cetiol HE (Henkel Corp.), Glucam P20 (Amerchol),Polyox WSR N-10 (Union Carbide), Polyox WSR N-3000 (Union Carbide),Luviquat (BASF), Finsolv SLB 101 (Finetex Corp.), mink oil, allantoin,stearyl alcohol, Estol 1517 (Unichema), and Finsolv SLB 201 (FinetexCorp.).

An emollient can also be applied to a surface of the article prior to orafter wetting with the wetting composition. Such an emollient may beinsoluble in the wetting composition and can be immobile except whenexposed to a force. For example, a petrolatum-based emollient can beapplied to one surface in a pattern, after which the other surface iswetted to saturate the wipe. Such a product could provide a cleaningsurface and an opposing skin treatment surface.

The emollient composition in such products and other products of thepresent invention can comprise a plastic or fluid emollient such as oneor more liquid hydrocarbons (e.g., petrolatum), mineral oil and thelike, vegetable and animal fats (e.g., lanolin, phospholipids and theirderivatives) and/or a silicone materials such as one or more alkylsubstituted polysiloxane polymers, including the polysiloxane emollientsdisclosed in U.S. Pat. No. 5,891,126, issued Apr. 6, 1999 to Osborn, IIIet al. Optionally, a hydrophilic surfactant may be combined with aplastic emollient to improve wettability of the coated surface. In someembodiments of the present invention, it is contemplated that liquidhydrocarbon emollients and/or alkyl substituted polysiloxane polymersmay be blended or combined with one or more fatty acid ester emollientsderived from fatty acids or fatty alcohols.

In an embodiment of the present invention, the emollient material is inthe form of an emollient blend. Desirably, the emollient blend comprisesa combination of one or more liquid hydrocarbons (e.g., petrolatum),mineral oil and the like, vegetable and animal fats (e.g., lanolin,phospholipids and their derivatives), with a silicone material such asone or more alkyl substituted polysiloxane polymers. More desirably, theemollient blend comprises a combination of liquid hydrocarbons (e.g.,petrolatum) with dimethicone or with dimethicone and other alkylsubstituted polysiloxane polymers. In some embodiments of the presentinvention, it is contemplated that blends of liquid hydrocarbonemollients and/or alkyl substituted polysiloxane polymers may be blendedwith one or more fatty acid ester emollients derived from fatty acids orfatty alcohols. PEG-7 glyceryl cocoate, available as Standamul HE(Henkel Corp., Hoboken, N.J.), can also be considered.

Water-soluble, self-emulsifying emollient oils, which are useful in thepresent wetting compositions, include the polyoxyalkoxylated lanolinsand the polyoxyalkoxylated fatty alcohols, as disclosed in U.S. Pat. No.4,690,821, issued Sep. 1, 1987 to Smith et al. The polyoxyalkoxy chainsdesirably will comprise mixed propylenoxy and ethyleneoxy units. Thelanolin derivatives will typically comprise about 20-70 suchlower-alkoxy units while the C₁₂-C₂₀-fatty alcohols will be derivatizedwith about 8-15 lower-alkyl units. One such useful lanolin derivative isLanexol AWS (PPG-12-PEG-50, Croda, Inc., New York, N.Y.). A usefulpoly(15-20)C₂-C₃-alkoxylate is PPG-5-Ceteth-20, known as Procetyl AWS(Croda, Inc.).

According to one embodiment of the present invention, the emollientmaterial reduces undesirable tactile attributes, if any, of the wettingcomposition. For example, emollient materials, including dimethicone,can reduce the level of tackiness that may be caused by theion-sensitive binder or other components in the wetting composition,thus serving as a detackifier.

Desirably, the wetting composition contains less than about 25 weightpercent of emollients based on the total weight of the wettingcomposition. More specifically, the wetting composition may compriseless than about 5 weight percent emollient, and most specifically lessthan about 2% emollient. More desirably, the wetting composition maycontain from about 0.01 weight percent to about 8 weight percent ofemollients. Even more desirably, the wetting composition may containfrom about 0.2 weight percent to about 2 weight percent of emollients.

In one embodiment, the wetting composition and/or pre-moistened wipes ofthe present invention comprise an oil-in-water emulsion comprising anoil phase containing at least one emollient oil and at least oneemollient wax stabilizer dispersed in an aqueous phase comprising atleast one polyhydric alcohol emollient and at least one organicwater-soluble detergent, as disclosed in U.S. Pat. No. 4,559,157, issuedDec. 17, 1985 to Smith et al., the entirety of which is hereinincorporated by reference.

Surface Feel Modifiers

Surface feel modifiers are used to improve the tactile sensation (e.g.,lubricity) of the skin during use of the product. Suitable surface feelmodifiers include, but are not limited to, commercial debonders; andsofteners, such as the softeners used in the art of tissue makingincluding quaternary ammonium compounds with fatty acid side groups,silicones, waxes, and the like. Exemplary quaternary ammonium compoundswith utility as softeners are disclosed in U.S. Pat. No. 3,554,862,issued to Hervey et al. on Jan. 12, 1971; U.S. Pat. No. 4,144,122,issued to Emanuelsson et al., Mar. 13, 1979, U.S. Pat. No. 5,573,637,issued to Ampulski et al. Nov. 12, 1996; and U.S. Pat. No. 4,476,323,issued to Hellsten et al., Oct. 9, 1984, the entirety of all of which isherein incorporated by reference. Desirably, the wetting compositioncontains less than about 2 weight percent of surface feel modifiersbased on the total weight of the wetting composition. More desirably,the wetting composition contains from about 0.01 weight percent to about1 weight percent of surface feel modifiers. Even more desirably, thewetting composition contains from about 0.01 weight percent to about0.05 weight percent of surface feel modifiers.

Fragrances

A variety of fragrances may be used in the wetting composition of thepresent invention. Desirably, the wetting composition contains less thanabout 2 weight percent of fragrances based on the total weight of thewetting composition. More desirably, the wetting composition containsfrom about 0.01 weight percent to about 1 weight percent of fragrances.Even more desirably, the wetting composition contains from about 0.01weight percent to about 0.05 weight percent of fragrances.

Fragrance Solubilizers

Further, a variety of fragrance solubilizers may be used in the wettingcomposition of the present invention. Suitable fragrance solubilizersinclude, but are not limited to, polysorbate 20, propylene glycol,ethanol, isopropanol, diethylene glycol monoethyl ether, dipropyleneglycol, diethyl phthalate, triethyl citrate, Ameroxol OE-2 (AmercholCorp.), Brij 78 and Brij 98 (ICI Surfactants), Arlasolve 200 (ICISurfactants), Calfax 16L-35 (Pilot Chemical Co.), Capmul POE-S (AbitecCorp.), Finsolv SUBSTANTIAL (Finetex), and the like. Desirably, thewetting composition contains less than about 2 weight percent offragrance solubilizers based on the total weight of the wettingcomposition. More desirably, the wetting composition contains from about0.01 weight percent to about 1 weight percent of fragrance solubilizers.Even more desirably, the wetting composition contains from about 0.01weight percent to about 0.05 weight percent of fragrance solubilizers.

Opacifiers

Suitable opacifiers include, but are not limited to, titanium dioxide orother minerals or pigments, and synthetic opacifiers such asREACTOPAQUE® particles (available from Sequa Chemicals, Inc., Chester,S.C.). Desirably, the wetting composition contains less than about 2weight percent of opacifiers based on the total weight of the wettingcomposition. More desirably, the wetting composition contains from about0.01 weight percent to about 1 weight percent of opacifiers. Even moredesirably, the wetting composition contains from about 0.01 weightpercent to about 0.05 weight percent of opacifiers.

pH Control Agents

Suitable pH control agents for use in the wetting composition of thepresent invention include, but are not limited to, malic acid, citricacid, hydrochloric acid, acetic acid, sodium hydroxide, potassiumhydroxide, and the like. An appropriate pH range minimizes the amount ofskin irritation resulting from the wetting composition on the skin.Desirably, the pH range of the wetting composition is from about 3.5 toabout 6.5. More desirably, the pH range of the wetting composition isfrom about 4 to about 6. Desirably, the wetting composition containsless than about 2 weight percent of a pH adjuster based on the totalweight of the wetting composition. More desirably, the wettingcomposition contains from about 0.01 weight percent to about 1 weightpercent of a pH adjuster. Even more desirably, the wetting compositioncontains from about 0.01 weight percent to about 0.05 weight percent ofa pH adjuster.

Although a variety of wetting compositions, formed from one or more ofthe above-described components, may be used with the wet wipes of thepresent invention, in one embodiment, the wetting composition containsthe following components, given in weight percent of the wettingcomposition, as shown in Table 2 below:

TABLE 2 Wetting Composition Components Wetting Composition Component:Weight Percent: Deionized Water about 86 to about 98 Activating compoundabout 1 to about 6 Preservative Up to about 2 Surfactant Up to about 2Silicone Emulsion Up to about 1 Emollient Up to about 1 Fragrance Up toabout 0.3 Fragrance solubilizer Up to about 0.5 pH adjuster Up to about0.2

In another embodiment of the present invention, the wetting compositioncomprises the following components, given in weight percent of thewetting composition, as shown in Table 3 below:

TABLE 3 Wetting Composition Components Class of Wetting Specific WettingComposition Composition Component Weight Component: Component: Name:Percent: Vehicle Deionized Water about 86 to about 98 Activating SodiumChloride about 1 to compound (Millport Ent., about 6 Milwaukee, WI)Preservative Glycerin, IPBC Mackstat H-66 Up to about 2 and DMDM(McIntyre Hydantoin Group, Chicago, IL) Surfactant Acyl Glutamate CS22Up to about 2 (Ajinomoto, Tokyo, Japan) Silicone Emulsion Dimethiconoland DC1785 Up to about 1 (Detackifier/Skin TEA (Dow Corning, Feel agent)Dodecylbenezene Midland, MI) Sulfonate Emollient PEG-75 Lanolin SolulanL-575 Up to about 1 (Amerchol, Middlesex, NJ) Fragrance FragranceDragoco Up to about 0.3 0/708768 (Dragoco, Roseville, MN) FragrancePolysorbate 20 Glennsurf L20 Up to about 0.5 solubilizer (Glenn Corp.,St. Paul, MN) pH adjuster Malic Acid to pH Up to about 0.2 5 (Haarman &Reimer, Tetrboro, NJ)

In another embodiment of the present invention, the wetting compositioncomprises the following components, given in weight percent of thewetting composition, as shown in Table 4 below:

TABLE 4 An Exemplary Wetting Composition Class of Wetting SpecificWetting composition composition Component Weight Component: Component:Name: Percent: Vehicle Deionized Water about 93 Activating SodiumChloride about 4 compound Preservative Glycerin, IPBC and Mackstat about1 DMDM Hydantoin H-66 Surfactant Acyl Glutamate CS22/ECS 22P about 1Silicone Dimethiconol and DC 1784/ about 0.5 Emulsion TEA DC 1785Dodecylbenezene Sulfonate Emollient PEG-75 Lanolin Solulan L- 575 about0.25 Fragrance Fragrance Dragoco about 0.05 Fragrance 0/708768 FragrancePolysorbate 20 Glennsurf L20 about 0.25 solubilizer pH adjuster MalicAcid to pH 5 about 0.07

It should be noted that the above-described wetting compositions of thepresent invention may be used with any one of the above-describedion-sensitive binder compositions of the present invention. Further, theabove-described wetting compositions of the present invention may beused with any other binder composition, including conventional bindercompositions, or with any known fibrous or absorbent substrate, whetherdispersible or not.

Strength Properties

Unless otherwise specified, tensile testing is performed according tothe following protocol. Testing of dry product should be conducted underTappi conditions (50% relative humidity, 73° F.) with a proceduresimilar to ASTM-1117-80, section 7. Tensile tests are performed with aconstant crosshead speed tensile tester such as the Thwing Albert1256-100 tensile tester with an RSA-2 10-kg load cell. Specimens are cutto 3-inch widths and 6 inch lengths, and mounted between jaws with a4-inch gauge length. The crosshead speed is 12 inches per minute. Peakload (for tensile strength) and elongation at peak load (for stretch)are measured. For cross direction (CD) tensile tests, the sample is cutin the cross direction. For machine direction (MD) tensile tests, thesample is cut in the cross direction.

Tensile tests in the dry state are reported for webs taken prior toapplication of the wetting composition. The machine direction drytensile strength is abbreviated as “MDDT,” and the cross direction drytensile strength as “CDDT.” The results can be reported as kg/3-in orconverted to units of g/in or g/2.54 cm.

Based on the dry weight of the specimen cut to the appropriate size, anexcess amount of wetting solution (4% saline solution with no otheradditives, unless otherwise specified) is applied to reach a solutionadd-on of 250-400%. The wetted specimens are then immediately passedthrough an Atlas Lab Wringer (Atlas Electric Devices Company, Chicago,Ill. No. 10404 LW-1, no load) to uniformly distribute the solution inthe sample and gently remove the excess solution to achieve a finalsolution add-on of 200%. Several iterations or passes may be needed toreach the add-on target depending on the sample. The completed,pre-moistened samples are then bagged in plastic to prevent dry-outbefore testing.

Cross direction wet tensile tests (CDWT) or machine direction wettensile strength (MDWT) are performed as described above using thepre-moistened sample as is, after the sample has equilibrated by sittingovernight in a sealed plastic bag.

For tests related to strength loss in a premoistened web occurring afterexposure to a new solution, a container having dimensions of 200 mm by120 mm and deep enough to hold 1000 ml is filled with 700 ml of theselected soak solution. No more than 108 square inches of sample aresoaked in the 700 ml of soaking solution, depending on specimen size.The premoistened specimens, that have equilibrated overnight, areimmersed in the soak solution and then allowed to soak undisturbed for aspecified time period (typically 1 hour). At the completion of the soakperiod, samples are carefully retrieved from the soak solution, allowedto drain, and then tested immediately as described above (i.e., thesample is immediately mounted in the tensile tester and tested, withoutbeing passed through the wringer). In cases with highly dispersiblematerials, the samples often cannot be retrieved from the soakingsolution without falling apart. The soaked tensile values for suchsamples are recorded as zero for the corresponding solution.

For the deionized soaked cross-direction wet tensile test, S-CDWT, thesample is immersed in deionized water for 1 hour and then tested. Forthe hard-water soaked cross-direction wet tensile test, S-CDWT-M (Mindicating divalent metal ions), the sample is immersed in watercontaining 200 ppm of Ca⁺⁺/Mg⁺⁺ in a 2:1 ratio prepared from calciumchloride and magnesium chloride, soaked for one hour and then tested.For the medium hard water soaked cross-direction wet tensile test,MS-CDWT-M, the sample is immersed in water containing 50 ppm ofCa⁺⁺/Mg⁺⁺ in a 2:1 ratio, soaked for one hour and then tested. Testingdone with other time increments or soaking solutions should be soindicated to prevent confusion with the S-CDWT or S-CDWT-M tests.

In one embodiment of the present invention, wet wipes are produced usingthe above-described wetting composition in Table 3 and an air-laidfibrous material comprising about 80 weight percent of bleached kraftfibers and 20 weight percent of any one of the above-describedion-sensitive binder compositions of the present invention, wherein theweight percentages are based on the total weight of the dry nonwovenfabric. In a further embodiment of the present invention, wet wipes areproduced using the above-described wetting composition in Table 3 and anair-laid fibrous material comprising 90 weight percent of softwoodfibers and 10 weight percent of an ion-sensitive binder compositionscomprising acrylic acid terpolymers or a copolymer substantially free ofacrylic acid monomers, wherein the weight percentages are based on thetotal weight of the dry nonwoven fabric. The amount of wettingcomposition added to the nonwoven fabric, relative to the weight of thedry nonwoven fabric in these embodiments, is desirably about 180 percentto about 240 weight percent.

Desirably, the wet wipes of the present invention possess an in-use wettensile strength (CDWT) of at least 100 g/in, and a tensile strength ofless than about 30 g/in after being soaked in water having aconcentration of Ca²⁺ and/or Mg²⁺ ions of about 50 ppm for about onehour (MS-CDWT-M). More desirably, the wet wipes possess an in-use wettensile strength of at least 300 g/in (CDWT), and a tensile strength ofless than about 30 g/in after being soaked in water having aconcentration of Ca²⁺ and/or Mg²⁺ ions of about 50 ppm for about onehour (MS-CDWT-M). In a further embodiment, the wet wipes desirablypossess an in-use wet tensile strength of at least 200 g/in (CDWT), anda tensile strength of less than about 20 g/in after being soaked inwater having a concentration of Ca²⁺ and/or Mg²⁺ ions of about 200 ppmfor about one hour (S-CDWT-M). Even more desirably, the wet wipespossess an in-use wet tensile strength of at least 300 g/in, and atensile strength of less than about 20 g/in after being soaked in waterhaving a concentration of Ca²⁺ and/or Mg²⁺ ions of about 200 ppm forabout one hour (S-CDWT-M).

Desirably, the wet wipes treated with the binder material of the presentinvention including the acrylic acid terpolymer possess an in-use wettensile strength of at least 100 g/in for a 1 inch width sample in thecross machine direction when soaked with 10% to 400% by weight wet wipessolution containing more than 0.3% by weight monovalent ion (NaCl)concentration and a tensile strength of less than about 30 g/in afterbeing soaked in deionized water for about one hour. More desirably, thewet wipes treated with the binder material of the present inventionincluding the acrylic acid terpolymer possess an in-use tensile strengthof at least 200 g/in for a 1 inch width sample in the cross machinedirection when soaked with 10% to 400% by weight wet wipes solutioncontaining more than 0.3% by weight monovalent ion (NaCl) concentrationand a tensile strength of less than about 30 g/in after being soaked indeionized water for about one hour.

In a further embodiment, the wet wipes treated with the binder materialof the present invention including the sulfonate anion modified acrylicacid terpolymer desirably possess an in-use tensile strength of at least200 g/in for a 1 inch width sample in the cross machine direction whensoaked with 10% to 400% by weight wet wipes solution containing morethan 1% by weight monovalent ion (NaCl) concentration and a tensilestrength of less than about 30 g/in after being soaked in water having aconcentration of Ca²⁺ and/or Mg²⁺ ions of about 50 ppm for about onehour. Even more desirably, the wet wipes treated with the bindermaterial of the present invention including the sulfonate anion modifiedacrylic acid terpolymer possess an in-use tensile strength of at least200 g/in for a 1 inch width sample in the cross machine direction whensoaked with 10% to 400% by weight wet wipes solution containing morethan 1% by weight monovalent ion (NaCl) concentration and a tensilestrength of less than about 30 g/in after being soaked in water having aconcentration of Ca²⁺ and/or Mg²⁺ ions of about 200 ppm for about onehour.

Products with high basis weights or wet strengths than flushable wetwipes may have relatively higher wet tensile strength. For example,products such as pre-moistened towels or hard-surface cleaning wipes mayhave basis weights above 70 gsm, such as from 80 gsm to 150 gsm. Suchproducts can have CDWT values of 500 g/in or greater, with S-CDWT valuesof about 150 g/in or less, more specifically about 100 g/in or less, andmost specifically about 50 g/in or less, with similar ranges possiblefor S-CDWT-M.

Dispersibility

Prior efforts to measure dispersibility of webs, whether dry orpremoistened, have commonly relied on systems in which the web wasexposed to shear while in water, such as measuring the time for a web tobreak up while being agitated by a mechanical mixer. The constantexposure to shear offers an unrealistic and overly optimistic test forproducts designed to be flushed in a toilet, where the level of shear isweak and extremely brief. Once the product has passed through the neckof the toilet and entered a septic tank, shear rates may be negligible.Further, the product may not be fully wetted with water from the toiletbowl when it is flushed, or rather, there may not have been adequatetime for the wetting composition of the product to have been replacedwith the water of the toilet bowl when the momentary shear of flushingis applied. Thus, previous measurements of dispersibility could suggestthat a product is dispersible when, in fact, it may be poorly suited forseptic system.

For a realistic appraisal of dispersibility, it is believed that arelatively static measure is needed to better simulate the low shearthat real products will experience once they have become fully wettedwith water from the toilet. Thus, a test method for dispersibility hasbeen developed which does not rely on shear and which provides animproved means of assessing suitability of a product for a septicsystem. In this method, the tensile strength of a product is measured inits original, wetted form (the CDWT measurement described above) andafter the product has been soaked in a second solution for one hour(either the S-CDWT or S-CDWT-M test). The second solution can be eitherdeionized water for determination of the “Deionized Dispersibility”value or hard water (according to the S-CDWT-M test) for determinationof the “Hard Water Dispersibility” value. In either case, theDispersibility is defined as (1 minus the ratio of the cross-directionwet tensile strength in the second solution divided by the originalcross-direction wet tensile strength)*100%. Thus, if a pre-moistenedwipe loses 75% of its CD wet tensile strength after soaking in hardwater for one hour, the Hard Water Dispersibility is (1−0.25)*100%=75%.The articles of the present invention can have a DeionizedDispersibility of 80% or greater, more specifically 90% or greater,specifically still 95% or greater, and can have a DeionizedDispersibility of about 100%. The articles of the present invention canhave a Hard Water Dispersibility of 70% or greater, more specifically80% or greater, specifically still about 90% or greater, and can have aDeionized Dispersibility of about 100%.

Method of Making Wet Wipes

The pre-moistened wipes of the present invention can be made in severalways. In one embodiment, the ion-sensitive polymer composition isapplied to a fibrous substrate as part of an aqueous solution orsuspension, wherein subsequent drying is needed to remove the water andpromote binding of the fibers. In particular, during drying, the bindermigrates to the crossover points of the fibers and becomes activated asa binder in those regions, thus providing acceptable strength to thesubstrate. For example, the following steps can be applied:

1. Providing an absorbent substrate that is not highly bonded (e.g., anunbonded airlaid, a tissue web, a carded web, fluff pulp, etc.).

2. Applying an ion-sensitive polymer composition to the substrate,typically in the form of a liquid, suspension, or foam.

3. Applying a co-binder polymer to the substrate.

4. Drying the substrate to promote bonding of the substrate. Thesubstrate may be dried such that the peak substrate temperature does notexceed 160° C., or 140° C., or 120° C., 110° C., or 100° C. In oneembodiment, the substrate temperature does not exceed 80° C. or 60° C.

5. Applying a wetting composition to the substrate.

6. Placing the wetted substrate in roll form or in a stack and packagingthe product.

Application of the co-binder polymer can be done simultaneously withapplication of the binder composition by previously mixing the two, orthe co-binder polymer can be added before or after the binder isapplied. The other steps are desirably conducted in the order shownabove.

Application of the ion-sensitive polymer composition to the substratecan be by means of spray; by foam application; by immersion in a bath;by curtain coating; by coating and metering with a wire-wound rod; bypassage of the substrate through a flooded nip; by contact with apre-metered wetted roll coated with the binder solution; by pressing thesubstrate against a deformable carrier containing the ion-sensitivepolymer composition such as a sponge or felt to effect transfer into thesubstrate; by printing such as gravure, inkjet, or flexographicprinting; and any other means known in the art.

In the use of foams to apply a binder or co-binder polymer, the mixtureis frothed, typically with a foaming agent, and spread uniformly on thesubstrate, after which vacuum is applied to pull the froth through thesubstrate. Any known foam application method can be used, including thatof U.S. Pat. No. 4,018,647, “Process for the Impregnation of a Wet FiberWeb with a Heat Sensitized Foamed Latex Binder,” issued Apr. 19, 1977 toWietsma, the entirety of which is herein incorporated by reference.Wietsma discloses a method wherein a foamed latex is heat-sensitized bythe addition of a heat-sensitizer such as functional siloxane compoundsincluding siloxane oxyalkylene block copolymers and organopolysiloxanes.Specific examples of applicable heat-sensitizers and their use thereoffor the heat sensitization of latices are described in the U.S. Pat.Nos. 3,255,140; 3,255,141; 3,483,240 and 3,484,394, all of which areincorporated herein by reference. The use of a heat-sensitizer is saidto result in a product having a very soft and textile-like hand comparedto prior methods of applying foamed latex binders.

The amount of heat-sensitizer to be added is dependent on, inter alia,the type of latex used, the desired coagulation temperature, the machinespeed and the temperatures in the drying section of the machine, andwill generally be in the range of about 0.05 to about 3% by weight,calculated as dry matter on the dry weight of the latex; but also largeror smaller amounts may be used. The heat sensitizer can be added in suchan amount that the latex will coagulate far below the boiling point ofwater, for instance at a temperature in the range of 35° C. to 95° C.,or from about 35° C. to 65° C.

Without wishing to be bound by theory, it is believed that a drying stepafter application of the binder solution and before application of thewetting composition enhances bonding of a fibrous substrate by drivingthe binder to fiber crossover points as moisture is driven off, thuspromoting efficient use of the binder. However, in an alternativemethod, the drying step listed above is skipped, and the ion-sensitivepolymer composition is applied to the substrate followed by applicationof the wetting composition without significant intermediate drying. Inone version of this method, the ion-sensitive polymer compositionselectively adheres to the fibers, permitting excess water to be removedin an optional pressing step without a significant loss of the binderfrom the substrate. In another version, no significant water removaloccurs prior to application of the wetting composition. In yet anotheralternative method, the ion-sensitive polymer composition and thewetting composition are applied simultaneously, optionally withsubsequent addition of salt or other activating compounds to activate orfurther activate the binder.

The present invention is further illustrated by the following examples,which are not to be construed in any way as imposing limitations uponthe scope thereof. On the contrary, it is to be clearly understood thatresort may be had to various other embodiments, modifications, andequivalents thereof which, after reading the description herein, maysuggest themselves to those skilled in the art without departing fromthe spirit of the present invention and/or the scope of the appendedclaims.

As used herein, the “thickness” of a web is measured with a 3-in acrylicplastic disk connected to the spindle of a Mitutoyo Digimatic Indicator(Mitutoyo Corporation, 31-19, Shiba 5-chome, Minato-ku, Tokyo 108,Japan) and which delivers a net load of 0.05 psi to the sample beingmeasured. The Mitutoyo Digimatic Indicator is zeroed when the disk restson a flat surface. When a sample having a size at least as great as theacrylic disk is placed under the disk, a thickness reading can beobtained from the digital readout of the indicator. Water-dispersiblesubstrates of the present invention can have any suitable thickness,such as from about 0.1 mm to 5 mm. For wet wipes, thicknesses can be inthe range of 0.2 mm to about 1 mm, more specifically from about 0.3 mmto about 0.7 mm. Thickness can be controlled, for example, by theapplication of compaction rolls during or after web formation, bypressing after binder or wetting composition has been applied, or bycontrolling the tension of winding when forming a roll good.

The use of the platen method to measure thickness gives an averagethickness at the macroscopic level. Local thickness may vary, especiallyif the product has been embossed or has otherwise been given athree-dimensional texture.

EXAMPLE 1 Preparation of Sulfonate Anion Modified Acrylic AcidTerpolymer

Acrylic acid (43.3 g, 0.60 mol), AMPS (10.7 g, 0.052 mol), butylacrylate (35.2 g, 0.27 mol), and 2-ethylhexyl acrylate (20 g, 0.11 mol)were dissolved in 55 g of acetone/water (70/30) mixture. An initiator,2,2-azobisisobutyronitrile (AIBN) (0.51 g, 3.1×10⁻³ mol), was dissolvedin 20 ml of acetone. The monomer solution was deoxygenated by bubblingN₂ through the solution for 20 minutes. To a 1000 ml three-neck roundbottom flask, equipped with a condenser, two addition funnels and amagnetic stirrer, was added 120 g of an acetone/water (70/30) mixture.The solvent was heated to gentle reflux under nitrogen. Monomers andinitiator were added simutaneously from the addition funnels over aperiod of two hours. Polymerzation was allowed to proceed for anadditional two hours, at the end of which the addition funnels andcondenser were replaced with a distillation head and a mechanical stirrod to remove acetone. A steady stream of N₂ was kept duringdistillation while the temperature was increased gradually from about65° C. to about 90° C. When the distillation was completed, 400 g ofdeionized water was added to reduce the viscosity of the polymersolution. A hazy, but uniform solution was obtained.

A total of nine polymers (Samples 1-9) were synthesized using theabove-described procedure. NaOH (2.1 g, 0.052 mol) in 20 ml of water wasadded at room temperature to neutralize the AMPS component in thesamples. The compositions of Samples 1-9 are summarized in Table 5below. All percentages are given in mole percent.

TABLE 5 Sulfonate Anion Modified Acrylic Acid Terpolymers Sample % AMPS% NaAMPS % AA % BA % EHA 1 0.0 3.0 64.0 22.5 10.5 2 0.0 3.5 63.5 22.510.5 3 0.0 3.9 62.1 24.6 9.4 4 0.0 4.0 57.0 26.5 12.5 5 0.0 4.2 64.719.7 11.4 6 0.0 5.0 58.0 26.5 10.5 7 0.0 4.0 63.0 21.5 11.5 8 0.0 5.059.0 25.5 10.5 9 0.0 5.0 60.0 24.5 10.5

EXAMPLE 2 Preparation of an Acrylic Acid Terpolymer

An acrylic acid terpolymer was produced using the polymerizationprocedure outlined in Example 2 of U.S. Pat. No. 5,312,883. Thefollowing monomers were used: acrylic acid (50 g, 0.69 mol), butylacrylate (25 g, 0.20 mol), and 2-ethylhexyl acrylate (25 g, 0.14 mol).The polymer was neutralized with 0.1 mole sodium hydroxide.

EXAMPLE 3 Preparation of Ion-sensitive Polymer Formulation

The polymers prepared in Table 5, Sample 9 and Example 2 above werecombined with Dur-O-Set RB to form the ion-sensitive polymerformulations of the present invention. The polymer formulations wereprepared as shown in Table 6 below.

TABLE 6 Ion-Sensitive Polymer Formulations % Terpolymer % ModifiedTerpolymer Sample (Example 2) (Table 5, Sample 9) % EVA 1 85.0 0.0 15.02 0.0 85.0 15.0 3 65.0 0.0 35.0 4 0.0 65.0 35.0 5 95.0 0.0 5.0 6 0.095.0 5.0 7 55.0 0.0 45.0 8 0.0 55.0 45.0 9 75.0 0.0 25.0 10 0.0 75.025.0

EXAMPLE 4 Solubility of Ion-sensitive Polymer Formulation

The sensitivity of the polymer formulations of Example 3 to divalentcations present in hard water were measured. Samples 1-10 of Example 3are placed in a number of CaCl₂ solutions with a Ca²⁺ concentrationvarying from <10 to 200 ppm. Following soaking for an hour, thesolubility of each polymer is noted. The solubility results are givenbelow in Table 7.

TABLE 7 Solubility Results Solubility in Ca²⁺ Sample <10 ppm 50 ppm 100ppm 200 ppm Sample 1 100 94 78 12 Sample 2 100 100 98 91 Sample 3 100 6036 2 Sample 4 99 100 97 90 Sample 5 100 97 88 19 Sample 6 100 100 99 90Sample 7 89 42 31 0 Sample 8 100 96 96 90 Sample 9 100 73 78 7 Sample 10100 100 100 90

In every case the film cast from the blend containing NaAMPS is moresoluble than the film containing the acrylic acid terpolymer, especiallyas the calcium ion concentration increases.

EXAMPLE 5 Testing the Binding Strength of Polymer Formulations with andwithout Crosslinking

For the pilot scale trials we used pulp based (CF 405 or NB 416 pulpform Weyerhaeuser) airlaid base-sheets bound together with 2-5% bicofibers. The bico fibers were either Type-255 (from KoSa Fibers ofSalisbury, N.C.) with an activated polyethylene sheath and a polyestercore or Danaklon fibers (from FiberVisions of Varde, Denmark) with apolyethylene sheath and a polypropylene core. Both kinds of bico fiberswere 2-3 denier and cut to 6 mm length. The binder formulations wereapplied by spraying 12-15 weight percent solutions on to both sides ofthe above base-sheet. The strengths of the base-sheets under variousconditions are reported after subtracting the base strength of the webdue to the bico fibers. Table 8 reports the strengths of the base-sheetswith different formulations in 0.4 weight percent NaCl (CDWT) as well asafter a one hour soak in deionized water (S-CDWT):

TABLE 8 Tensile Strength EVA Binder Oven S- % % Crosslinkable BW Add-OnTemp CDWT CDWT Sample Terpolymer EVA ? (gsm) (%) (° C.) (g/in) (g/in) 185 15 Yes 70 22 400 413 112 2 65 35 Yes 70 22 400 467 375 3 85 15 Yes 7123 400 444 116 4 85 15 Yes 76 28 400 518 143 5 85 15 No 70 22 400 430 216 85 15 Yes 73 25 350 336 60 7 65 35 Yes 67 18 350 332 237 8 65 35 Yes69 21 350 268 165 9 85 15 Yes 68 20 350 219 35 10 65 35 Yes 67 19 350199 74 11 85 15 No 69 21 350 226 20 12 65 35 No 67 19 350 196 29 BW:Basis Weight CDWT: Cross machine Direction Wet Tensile strength. S-CDWT:CDWT after soaking for one hour in deionized water.

All the above codes would wet out better on first insult relative to abinder formulation containing 100% acrylic acid terpolymer. Also, thebinder formulations which contain the EVA, spray much better than 100%acrylic acid terpolymer, leading to much improved binder distributionand penetration on the substrate. Significantly, those formulations thatwere not crosslinkable; i.e., Samples 5, 11 and 12, had S-CDWTs of lessthan 30 g/in.

EXAMPLE 6

Binder formulations are prepared having the compositions shown in Table9 below. The binder formulations at 12 weight percent solids are sprayedon both sides of an airlaid web. The airlaid web is based on pulp (CF405 from Weyerhaeuser). Table 9 shows the strength of the base-sheet in0.9% NaCl solution (CDWT) and after a one hour soak in deionized water(S-CDWT). The effect on strength after aging the samples in saltsolution over a period of up to 16 weeks is also shown. A preservative,such as Mackstat H66, is added to the samples to prevent mold growth onthe basesheets as they age in the salt solution.

TABLE 9 Tensile Strength of Base-Sheet % % BW Binder Add- Oven TempAging Time CDWT S-CDWT Sample Terpolymer EVA (gsm) On (%) (° C.) (Weeks)(g/in) (g/in) 1 85 15 73 25 440 0 488 14 2 85 15 73 25 440 16 393 11 365 35 64 25 440 0 358 16 4 65 35 64 25 440 12 369 21 5 55 45 64 25 440 0364 28 6 55 45 64 25 440 12 354 32

The results in Table 9 indicate that the web does not lose initialproperties even after extensive aging in the in-use salt solution whenDur-O-Set RB is used as the EVA. If a crosslinkable agent is present inthe EVA, lower dispersibility results after aging the samples for a fewweeks.

EXAMPLE 7

In FIG. 1 is shown the strength properties of the NaAMPS modifiedterpolymer, which is also dispersible in hard water (up to 200 ppmCa⁺⁺/Mg⁺⁺ solution). A base-sheet based on 75 weight percent NaAMPSmodified acrylic acid terpolymer (SSB) and 25 weight percent EVA(Dur-O-Set® RB) exhibits very good strength during use (in 1.5% or 4.0%NaCl solution) and disperses in very hard water. SSB-4 dispersed in hardwater in 10 minutes. SSB-5 dispersed in hard water in 3 hours.NaAMPS-SSB is more viscous relative to Lion-SSB.

Tensile results for Examples 5 through 7 were obtained with an MTStensile test device, the MTS 500/S unit (MTS Systems, Research Park,North Carolina) using the Testworks® 3.10 for Windows software. Insteadof the normal 3-inch strip for testing, a 1-inch wide strip was used,cut to 6 inches in length. The gauge length between the rubber-coatedjaws of the test device was 3 inches. Testing was operated at thespecified crosshead speed of 12 in/min. The MTS device with the modifiedtest procedure generally gives comparable results to the tensile testprotocol previously described using 3-inch wide samples and theThwing-Albert tester.

EXAMPLE 8

The addition of the co-binder polymer to the ion-sensitive polymerreduces the shear viscosity of the polymer blend compared to the shearviscosity of the ion-sensitive polymer alone. Table 10 illustrates theeffect of the addition of various co-binder polymers to an acrylic acidterpolymer (SSB-2) in accordance with the present invention.

TABLE 10 Effect of the Addition of Various Co-Binder Polymers to SSB-2Polymer Blend Viscosity @ 100 sec⁻¹ 18 weight percent SSB-2 solids Toohigh to measure: >100,000 cps 15 weight percent sodium polyacrylate10,000 cps solids (MW = 250,000, 50% neutralization) 12 weight percentneat SSB-2 80 cps 12 weight percent blend of 80 parts by wt. 25 cpsSSB-2 and 20 parts by wt. Rhoplex NW 1715K 12 weight percent blend of 80parts by wt. 28 cps SSB-2 and 20 parts by wt. Rovene 12 weight percentblend of 80 parts by wt. 20 cps SSB-2 and 20 parts by wt. Dur-O-Set RB

Table 10 shows that the addition of Rhoplex® NW 1715K, Rovene® 4817 andDur-O-Set® RB significantly reduce the shear viscosity of the SSB-2acrylic acid terpolymer alone. The reduction in viscosity is not due toa mere dilution of the SSB-2, because the addition of sodiumpolyacrylate resulted in a significant increase in the shear viscosityof the SSB-2.

EXAMPLE 9

Dried solid bars were prepared from Rhoplex® NW 1715K, Rovene® 4817 andDur-O-Set® RB. The bars were prepared by pouring a quantity of thepolymer into a rectangular silicone mold an open rectangular siliconemold 1 cm wide, 4 cm long, and 3 mm deep. The polymer in the mold wasthen heated at 60° C. overnight. The dried polymer in the mold was thenplaced in a container with 30 ml of deionized water at about 23° C. andallowed to sit for one hour. None of the bars were dispersed in thedeionized water.

Bar samples were then prepared from the sulfonate anion modified acrylicacid terpolymer (NaAMPS+SSB) blended separately with Rhoplex® NW 1715K,Rovene® 4817 and Dur-O-Set® RB. The polymer blends were made from 75% byweight sulfonate anion modified acrylic acid terpolymer and 25% byweight of the co-binder polymers. The bar samples were prepared in thesame manner as described above. The bar samples were then added todeionized water. Each of the bar samples made from the following polymerblends; i.e., NaAMPS+SSB/Rhoplex NW 1715K, NaAMPS+SSB/Rovene 4817 andNaAMPS+SSB/Dur-O-Set RB, dispersed in the deionized water within onehour.

EXAMPLE 10

A substrate in the form of an airlaid web was prepared on a commercialairlaid machine having a width of 66.5 inches. A DanWeb airlaid formerwith two forming heads was used to produce substrates having basisweights of about 60 gsm. Weyerhaeuser CF405 bleached softwood kraftfiber in pulp sheet form was used and fiberized in a hammermill, thenformed into an airlaid web on a moving wire at a speed of 200 to 300feet per minute. The newly formed web was densified by heated compactionrolls and transferred to a second wire, where the web was humidifiedwith an atomized spray of water applying an estimated 5% moisture add onlevel immediately prior to a second heated compaction roll to furtherdensify the web. The web was then transferred to an oven wire andsprayed on the top side with ion-sensitive polymer formulation mixtureon the exposed surface of the web, applying 10% ion-sensitive polymerformulation solids relative to the dry fiber mass of the web.

The ion-sensitive polymer formulation mixture comprised water as thecarrier with 12% binder solids, wherein the binder comprised 75% SSB-4as the ion-sensitive polymer formulation and 25% Rhoplex® NW-1715K latexemulsion (Rohin and Haas Corp.) as the co-binder polymer.

Spray was applied with a series of Quick Veejet® nozzles, Nozzle No.730077, manufactured by Spraying Systems Co. (Wheaton, Ill.), operatingat 95 psi. A spray boom over the web provided 13 such nozzles on5.5-inch centers with a tip-to-wire distance of 8 inches. Thisarrangement yields 100% overlap of spray cones for the ion-sensitivepolymer formulation solution of this trial.

After the web was sprayed, it was carried into an oven with through-flowof air at about 225° C. to dry the binder solution. The web then wastransferred onto the underside of another oven wire, upon which itpassed over another spray boom where more ion-sensitive polymerformulation solution was applied to the bottom side of the web to addanother 10 weight percent solids relative to the dry fiber mass of theweb. The web then passed through two successive dryer units wherethrough-air drying with air at about 225° C. completed drying of theweb. The pressure differential across the web was approximately 10inches of water. The length of the three dryer sections, from first tothird, respectively, was about 9, 10, and 6 feet.

The thickness of the web after drying was 1.14 mm (this number, likeother physical properties reported here, can vary depending on thefibers, basis weight, and so forth). The machine direction dry tensile(MDDT) strength of the web was measured at 4.59 kg/3 in. The crossdirection dry tensile (CDDT) strength of the web was measured at 3.82kg/3 in with a CD stretch of 8.98%.

The dried and treated web was then trimmed to 60 inches width, reeledand later slit into 4-inch wide rolls, which were then treated withwetting composition and formed into coreless rolls suitable for use as apre-moistened bath wipe. The wetting composition was sprayed uniformlyon one side of the 4-inch wide web prior to reeling the web into rollssuitably sized for use. The wetting composition was 4 weight percentNaCl in deionized water.

The cross direction wet tensile (CDWT) at 4 weight percent saline wasmeasured at 0.76 kg/3 in. The Soaked CDWT strength was effectively 0, aswas the Soaked CD Stretch, meaning the sheet was fully dispersible.

EXAMPLE 11

The sheet formed was identical to that of Example 10 except that thefibers in the airlaid web were 75% softwood kraft and 25% PET fibers.The thickness of the web after drying was 1.35 mm. The machine directiondry tensile (MDDT) strength of the web was measured at 3.87 kg/3 in. Thecross direction dry tensile (CDDT) strength of the web was measured at2.84 kg/3 in with a CD stretch of 11.31%. The cross direction wettensile (CDWT) at 4% saline was measured at 0.82 kg/3 in. The SoakedCDWT strength was effectively 0, as was the Soaked CD Stretch.

EXAMPLE 12

Additional examples were conducted according to Example 10, with theexception that Rovene latex emulsion was used as the co-binder polymerand the basis weight and fiber composition varied as shown in Table 11.The Soaked CDWT results were all 0, indicating a complete loss oftensile strength. Other results are shown in Table 11, where Pulp/PETdesignates the ratio of softwood to synthetic fibers in the substrate,BW is the basis weight in gsm, TH is the thickness in mm, and S-CDWT-Mis the one-hour soak CD wet tensile test for a sample soaked in watercontaining 200 ppm of Ca⁺⁺/Mg⁺⁺ in a 2:1 ratio.

TABLE 11 Measurements for Examples 3A-3F. S- Run Pulp/PET BW TH MDDTCDDT CDWT CDWT-M 3A 100/0  60.3 1.18 5.44 4.12 0.69 0 3B 85/15 62.9 1.254.68 4.23 0.66 0 3C 75/25 55.6 1.04 5.48 4.06 0.66 0 3D 75/25 59.3 1.194.87 3.96 0.81 0.17 3E 75/25 60.7 1.48 4.41 3.51 0.79 0.12 3F 85/15 62.71.46 4.6 3.82 0.76 0

The non-zero S-CDWT-M values (soaked wet tensile in hard water) arenon-zero for two trials with 25% PET fibers, suggesting that higheramounts of synthetic fibers can begin to compromise waterdispersibility.

EXAMPLE 13

A pre-moistened wipe was made similar to that of Example 10, except thatthe co-binder polymer was a modified Elite® latex emulsion substantiallyfree of crosslinking agents provided by National Starch. The basisweight of the web was 61.35, the thickness 1.21 mm, the MDDT 5.09kg/3-in, the MD stretch 7.89%, the CDDT 3.90 kg/3-in, the CD stretch9.50%, the CDWT in 4% saline 0.78 kg/3-in, the CDWT stretch 32.96%, andthe residual strengths after one hour in both deionized water (S-CDWT)and hard water (S-CDWT-M) were 0 kg/3-in.

EXAMPLE 14 Particulate Addition

Pre-moistened wipes comprising the basesheet of Example 10 were preparedwith a wetting composition comprising a slurry of particles. Theparticles were selected from the following products marketed byPresperse, Inc. (Piscataway, N.J.):

TABLE 12 Particles from Presperse, Inc. selected for use inpre-moistened wipes Name Composition Characteristics MCP-45 Mica andpolymethyl Fine powder, platelets methacrylate coated with microspheres,13-17 microns Sericite SL-012 98% mica, 2% methicone Fine white powder,hydrophobic surface, 2-10 microns Rose talc Talc White powder, 10-12microns Permethyl 104A Iso-octahexacontane (polyisobutene) Cashmir K-IIMica (97%), silica beads Fine white powder, (3%), 0.3 microns plateletscoated with microspheres, 10-14 microns Synthecite Syntheticfluorphogopite Fine powder, FNK-100 10-15 microns Ganzpearl GMX- Methylmethacrylate Spherical powder, 4.5-8.5 0610 crosspolymer micronsGanzpearl Styrene/divinylbenzene White powder, 4.5-8.5 GS-0605 copolymermicrons Ganzpearl PS-8F Styrene/divinylbenzene 0.4 microns copolymerSpheron N-2000 Amorphous silica White powder, 2-15 microns, low oilabsorption Spheron L-1500 Amorphous silica White powder, 3-15 microns,high oil absorption

For each particle type in Table 12, five 1000-gram batches of wettingcomposition were prepared with particle concentrations of 0.5%, 1%, 2%,5%, and 10% by weight. Each batch was prepared by adding the appropriateamount of deionized, filtered water to a 1.15-liter beaker (for the 5batches, the water amounts were, respectively, 926.3 g, 921.3 g, 911 g,881 g, and 831 g). A 2.5-inch magnetic stirring rod stirred the contentsof the jar while residing on a Thermolyne Cimarec 2 stirrer, withstirring speed set to maximum to provide a strong central vortex in eachof 5 jars. Each batch comprised 4 weight percent sodium chloride, addedto the water as 40 g of salt; 1 weight percent (10 g) Amisoft ECS22-Pacylglutamate surfactant (Ajinomoto, Tokyo, Japan); 0.5 weight percent(5 g) DC silicone emulsion (Dow Corning) added to the salt water andsurfactant; 1 weight percent (10 g) Mackstat H 66 preservative (McIntyreGroup, Chicago, Ill.); and 0.05 weight percent (0.5 g) of fragrancefirst mixed into 0.25 weight percent (2.5 g) of polysorbate 20, thenmixed into the solution comprising the previous ingredients; and therespective amount of powder (from 0.5 to 10, weight percent or from 5 gto 100 g). The powder was added to the solution as it was being stirredand allowed to wet and become suspended over a period of about 30minutes after addition of the powder. Some additional stirring by handwas needed for some of the powders to promote mixing. Once the powderwas dispersed in the liquid, the pH was adjusted to 5.0 by adding malicacid, prepared at a strength of 50 weight percent in water. The pH wasmeasured with a Cole Parmer Model 59002-00 pH/mV/° C. meter, with aModel 59002-72 KK8 electrode.

Each of the particle suspensions was then added to dried airlaidbasesheets that had been treated with NaAMPS binder and a co-binderpolymer according to Example 13. The add level was 200%, withapplication by spray on one side of the web. The moistened web was thensealed in plastic to sit overnight. Examination of the pre-moistenedwipes treated with particulate suspensions as the wetting compositionrevealed that the particles generally remained in the wet wipe withoutthe need for additional thickeners or polymeric retention aids.Squeezing the pre-moistened wipes, for example, yielded a mostly clearfluid apparently substantially devoid of particulates, in contrast tothe milky suspensions used to wet the wipes. Generally, no visibleresidue appeared to be left of the hands after using the wipes. Theparticulates also generally improved opacity and appeared to slightlyprovide tactile property improvements (reduced tack, better rheologicalfeel).

EXAMPLE 15

The role of ungelled starch particles in the wetting composition of thepresent invention was investigated as a means of reducing tackiness andimproving surface feel for a pre-moistened wipe. Five wettingcompositions containing tapioca starch were prepared according to theformulations in Table 13. Softwood airlaid webs according to Example 10were wetted with the wetting composition with a 300% add-on level. (QSmeans “quantity sufficient” to achieve the desired pH).

TABLE 13 Formulations for five wetting compositions containing starchWater Phase A B C D E Water (Tap) 76.9 71.9 68.9 66.9 96.45 Laponite XLS2 2 2 2 Phospholipid CDM 0.5 Malic Acid (50% 7 7 7 7 Solution) to pH 4Tapioca 28-1810 10 15 18 20 DC 1784 1 1 1 1 Dragoco Fragrance 0.1 0.10.1 0.1 0.05 0/708768 Mackstate H 66 0.5 0.5 0.5 0.5 0.5 Sodium Chloride1.5 1.5 1.5 1.5 1.5 Mackam 2C 1 1 1 1 1 Malic Acid (50% QS QS QS QS QSSolution) to pH 4

The pre-moistened wipes comprising starch displayed reduced tackinesswhen handled with the human hand than did similar pre-moistened wipeswithout the starch. The wipes containing starch also felt smoother.

EXAMPLE 16

Additional pre-moistened wipes were prepared using the wettingcompositions displayed in Table 14, one of which comprised starch as anadditive and the other which comprised botanicals. The wettingcomposition was added to an airlaid fibrous substrate comprising anion-sensitive binder. The wetting composition was added at add-on levelsof 300 and 200 weight percent, respectively.

TABLE 14 Formulations for two wetting compositions Code Starch Botanicalformula # 1 2 Raw Materials Water Phase Water (Tap) 61.4 95.45 LaponiteXLS 2 Phospholipid CDM 0.5 Malic Acid (50% 7 Solution) to pH 4 Tapioca28-1810 25 DC 1784 1 0.5 Dragoco Fragrance 0.1 0.05 0/708768 Mackstate H66 1 0.5 Sodium Chloride 1.5 1.5 Mackam 2C 1 Malic Acid (50% Solution)QS QS to pH 4 CS-22 0.5 Emulgin G 0.5 Witch Hazel 0.5 100 100 pH-FinalSolution add-on 300% 200%

EXAMPLE 17 Binder Specifications

A variety of ion-sensitive binders were prepared comprising acrylic acid(AA), butacrylic acid (BA), 2-ethylhexyl-acrylic acid, and AMPS, withthe mole percents and molecular weights shown in Table 15:

TABLE 15 Ion-sensitive binders comprising AMPS SSB Mole percent ofmonomers: Code MW × 10⁻⁶ AA BA 2-EHA AMPS A 1.54 60 24.5 10.5 5 B 1.3260 24.5 10.5 5 C 0.604 60 24.5 10.5 5 D 0.548 60 24.5 10.5 5 E 0.609 6024.5 10.5 5 F 0.545 60 24.5 10.5 5 G 1.21 62 24.5 8.5 5 H 0.79 60 24.510.5 5 I 0.916 60 24.5 10.5 5 J 0.71 60 24.5 10.5 5 K 0.786 60 24.5 10.55 L 0.845 60 24.5 10.5 5 M 0.640 60 24.5 10.5 5 N 0.800 60 24.5 10.5 5 00.635 60 24.5 10.5 5 P 0.610 60 24.5 10.5 5 Q 0.575 60 24.5 10.5 5 R0.638 60 24.5 10.5 5 S 0.912 62 26.5 7.5 4 T 0.609 60 25.5 10.5 4 U0.835 58 27 10 5 V 0.675 58 27 10 5 W 0.734 58 27 10 5 X 0.716 58 27 105 Y 0.650 58 27 10 5 Z 0.718 58 27 10 5 AA 0.518 58 27 10 5 AB 0.544 5827 10 5

These binders were prepared according to the methods of Example 1, butscaled up as a batch process capable of producing several hundredgallons per batch.

EXAMPLE 18 Typical Wetting Solution

A wetting composition was prepared by combining the followingingredients according to the specific weight percent: 92.88 weightpercent deionized water, 4 weight percent NaCl, 1 weight percentMackstat H-66 preservative (McIntyre Group, Chicago, Ill.), 1 weightpercent CS22 acyl glutamate anionic surfactant (Amisoft Corp., Tokyo,Japan), 0.5 weight percent DC 1785 silicone emulsion (Dow Corning), 0.25weight percent Solulan L-575 (PEG-75 lanolin, available from Amerchol, adivision of Union Carbide), 0.05 weight percent Dragoco fragrance0/708768 (Dragoco SA, Cuautitlán Izcalli, D.F. Mexico, Mexico), 0.25weight percent polysorbate 20, and about 0.07 weight percent of 50percent by weight malic acid solution to bring the pH to 5.0.

EXAMPLE 19 A Treated Substrate

An airlaid substrate was made with the equipment described for Example10. Basis weight was 65 gsm and the fibers were 100% Weyerhaeuser CF405bleached softwood kraft pulp. The binder solution had 12.8 weightpercent binder solids, 75 weight percent of which was SSB Code H ofTable 15 and 25 weight percent Dur-O-Set RB latex co-binder (NationalStarch). The binder solution was sprayed onto the web as described inExample 1, with the dryer air temperature at 215° C. for all three ovensections.

EXAMPLE 20 A Treated Substrate

An airlaid substrate was made according to Example 10, except that thebasis weight was 63 gsm and the oven temperature was 227° C. Reel speedwas 197 fpm. Thickness of the dried web was 1.30 mm.

MDDT was 5.55 kg/3-in, CCDT was 4.83 kg/3-in, CDWT (in 4% NaCl solution)was 1.07 kg/3-in, and S-CDWT as well as S-CDWT-M (1 hour soak tests)gave 0 kg/3-in.

Some of the dried web was slit to a 4.25-inch width and treated withwetting composition at 225% add-on, comprising 4% NaCl in deionizedwater without surfactant. The moistened web was perforated with aperf-knife operating with a depth of 0.070 inches to perforate every 4.5inches. The perforated web was rolled into a coreless roll with 100perforated sheets per roll (approximately 37.5 feet per roll) and placedin a white plastic cartridge for subsequent use in a dispenser forpre-moistened wipes.

EXAMPLE 21

A portion of the dried, treated web of Example 20 was wetted with thewetting composition of Example 18 and converted into perforate roll formfor use as pre-moistened wipes to be dispensed from a bathroomdispenser.

Comparative Example 22

A conventional, adhesively bonded airlaid substrate with a basis weightof 60.1 gsm was created using the methods described in Example 10.Dur-O-Set E-646 (National Starch) was used with wood pulp (CF405) Thesubstrate was wetted with a 4% NaCl solution and tested using themethods described. The binder was entirely the self-crosslinkingDur-O-Set E-646 compound; no salt-sensitive binder was applied. Thebinder solids mass was 17% of the substrate mass. Dry thickness of theweb was 1.4 mm, and the CDWT value was 1.3 kg/3-in, while S-CDWT was 1.2kg and S_CDWT-M was 1.15 kg, indicating that the web maintained nearlyall of its strength after soaking, and suggesting that the crosslinkedlatex provided the majority of the tensile strength of the web and thatthe latex bonds did not weaken substantially in water.

EXAMPLE 23

A variety of binder/co-binder combinations were prepared, as describedbelow, using the salt-sensitive binders of Table 15 and co-binders asshown in Table 16 which are not self-crosslinkable.

TABLE 16 Latex co-binders that are not self-crosslinkable. Co-binder IDCo-binder Manufacturer 1 Dur-O-Set RB National Starch 2 Rhoplex NW-1715KRohm and Haas 3 Rovene 4817 Mallard Creek

Using the methods described in Example 10, airlaid substrates were madefrom bleached kraft fibers. The substrate was wetted with a 4% NaClsolution and tested using the methods described. All substrates werecomprised of wood pulp (CF405) and binder. Results are shown in Table17, where the binder mixture consistently comprised 75% of asalt-sensitive binder selected from Table 15 and 25% of a co-binderselected from Table 16. The binder/co-binder column refers to the binderand co-binders listed in Table 15 and 16, respectively. For example,“A/1” refers to a mixture of SSB Code A in Table 15 and co-binder 1 ofTable 16.

TABLE 17 Tensile data for various binder systems. % Binder/ SSB BWThick. CDWT S-CDWT S-CDWT-M S-CDWT-M3 Binder Cob. MW × 10⁻⁶ (gsm) (mm)(kg/3″) (kg/3″) (kg/3″) 3 hrs (kg/3″) 16.7 A/1 1.54 71.3 1.46 0.990 00.330 0.180 20 B/1 1.32 63.3 1.25 1.242 0.163 0.470 0.310 20 B/1 1.3266.6 1.46 1.040 0 0.230 0.550 20 G/1 1.21 62.2 1.20 1.002 0 0.270 0 20H/1 0.79 63.1 1.3 1.070 0 0 0 16.7 C/1 0.604 73.6 1.59 0.750 0 0 0 20C/1 0.604 71.2 1.5 0.900 0 0 0 20 C/1 0.604 61.1 1.28 1.140 0 0 0 20 D/10.548 62.5 1.32 0.900 0 0 0

As seen in Table 17, nearly all of the substrates have lost more that80% of their tensile strength after soaking in deionized water for 1hour (S-CDWT). The substrates have lost more that 60% of their strength(S-CDWT-M) after soaking for 1 hour in a solution of 200 ppm of divalentcations (Ca++/Mg++ 2:1). In particular, for the runs shown in Table 17,the samples completely lost their strength in 1 hour in the 200 ppmsolution when the molecular weight of the salt sensitive binder was lessthan 1,200,000. After 3 hours of soak time in the 200 ppm divalentcation solution, the SSBs with high molecular weight have generally lostmore of their strength, but may still have non-zero tensile strength.

By comparison, the comparative Example 22 lost less than 15% of itsstrength after soaking for 1 hour in either deionized water or 200 ppmdivalent ion solution. All of the substrates in Table 17 lost moretensile strength on soaking than the comparative Example 22.

EXAMPLE 24

Different co-binders from Table 16 were blended with the salt-sensitivebinder Code F from Table 15. The binder blend was then applied using themethods described in Example 10 to create the airlaid substrates listedin Table 18. In each case, 20% binder solids were applied to thesubstrate in a blend of 75% SSB/25% co-binder

TABLE 18 Tensile data for various co-binder systems. S- Binder/Co-binder BW Thick, CDWT S-CDWT CDWT-M Co-binder Used (gsm) (mm) (kg/3″)(kg/3″) (kg/3″) F/1 Dur-O-Set 59.77 1.06 0.735 0 0 RB F/2 Rhoplex 60.831.14 0.758 0 0 F/3 Rovene 60.28 1.18 0.687 0 0

Under similar run conditions, all three co-binders perform comparably.All of the substrates have lost their tensile strength (S-CDWT-M) in the200 ppm divalent cation solution independent of co-binder type.

EXAMPLE 25

Measurements were made of the peel force required to unroll the productfrom the outer layers of a coreless roll of pre-moistened wipes suitablefor use as a moist toilet paper product. The product was made accordingto Example 10 with an add-on level of 200% wetting composition. Thedried web was slit to a 4.25-inch width and treated with wettingcomposition at 200% add-on, comprising 4% NaCl in deionized water withsurfactants, silicone, and lanolin as listed in Table 19 for wettingcomposition Q, R, and S. The moistened web was perforated with aperf-knife operating to perforate every 4.5 inches. The perforated webwas rolled into a coreless roll with 100 perforated sheets per roll(approximately 37.5 feet per roll) and sealed in a plastic cartridge forsubsequent use in a dispenser for pre-moistened wipes.

TABLE 19 Other additives in three wetting compositions. SiliconeAcylglutamate Solution emulsion Lanolin surfactant Q 0.50% 0.25% CS22 R1.00% 0.25% ECS 22P S 1.00% 0% ECS 22P

The roll rested freely in a plastic tub with a rounded, ribbed bottomthat held the roll in place with a minimum of friction when the roll wasunwound by pulling vertically upwards on the tail end of the roll.Adjacent plies adhered to each other such that some force was requiredto separate the layers. The peel force needed was less than the weightof the roll and appeared to be substantially greater than the frictionalresistance offered by the tub as the roll turned, evidenced in part byangle between the web and the roll at the point of separation. With nopeel force, the angle between the web being pulled up and a line normalto the roll at the point of separation would be 90 degrees, but inunwinding the moist roll with the salt-sensitive binder, the angle wassubstantially less than 90 degrees, thus imparting peel force toseparate the web.

The peel force was measured with an MTS Sintech 1/G test machine withTestWorks 3.10 software. All testing as done in a conditioned laboratoryunder Tappi Standard conditions. A 4.5-inch wide clamp with rubbersurfaces gripped the tail of a roll, with the roll position directlyunderneath the clamp such the tail would remain vertical as it wasunwound from the roll if there were no peel force causing the web towrap a portion of the roll and deflect from the vertical. The clamp wasattached to the crosshead, which pulled the tissue web upward at a speedof 100 cm/minute. Peel force was measured by a 50 N load cell. Theaverage load to pull 18 sheets away from the roll was recorded byaveraging two runs in which 4 sheets each were separated and two runs inwhich 5 sheets each were separated. Only the first 18 sheets from theroll were used in the measurement. The average peel force for two rollsper condition (for an overall average taken over a total of 36 sheets)is reported in Table 20 below.

TABLE 20 Peel force in grams to remove a web from a wound moist roll.Thickness, Binder MDWT, Peel force, BW, gsm mm add-on Solution g/in g 651.1 22% Q 500 167 65 1.1 22% R 475 170 65 1.1 22% S 533 162 60 0.76 20%Q 438 131 55 0.76 20% Q 353 106 55 0.76 20% R 341 120 55 0.84 20% R 385115

Peel forces for a roll having a width between 7 and 15 cm (the width ofthe rolls tested in Table 20 are 10.8 cm) are desirably are less than500 g, more specifically less than 300 g, more specifically less thanabout 200 g, more specifically still less than about 160 g, mostspecifically less than about 120 g, with an exemplary range of fromabout 50 g to about 350 g, or from about 80 g to about 200 g. Moregenerally, the peel force per 4-inch width of a moist roll can be any ofthe aforementioned values of ranges.

EXAMPLE 26

Additional samples were prepared according to Example 24 above, exceptthat 15 weight % of the fiber blend consisted of 6-mm, crimped PETfibers (KoSa). Different co-binders from Table 16 were blended with thesalt-sensitive binder Code F from Table 15. The binder blend was thenapplied using the methods described in Example 10 to create the airlaidsubstrates whose properties are listed in Table 21. In each case, 20%binder solids were applied to the substrate in a blend of 75% SSB/25%co-binder. The properties of these substrates were measured afterwetting with a 4% NaCl solution. All three co-binders performcomparably. All of the substrates have lost their tensile strength in200 ppm divalent cation solution independent of co-binder type. Comparedto the parallel results in Example 24, incorporation of the syntheticfibers impart a slight to modest strength improvement (CDWT) and amodest increase in dry bulk.

TABLE 21 Data for substrates with PET fibers and various co-binders. S-Binder/ Co-binder BW Thick, CDWT S-CDWT CDWT-M Co-binder Used (gsm) (mm)(kg/3″) (kg/3″) (kg/3″) F/1 Dur-O-Set 63.32 1.31 0.782 0 0 RB F/2Rhoplex 62.07 1.35 0.820 0 0 F/3 Rovene 62.90 1.25 0.660 0 0

EXAMPLE 27

Additional examples were conducted according to Example 26 withincreasing amounts of synthetic fiber being added to the fiber blend.Either a 6 mm crimped PET fiber (KoSa) or a 6 mm, crimped 2.4 dtex,Lyocell fiber was used as noted in Table 22 below. The binder blend wasa constant blend of 75% SSB and 25% co-binder.

TABLE 22 Data for substrates with PET fibers and various co-binders.Binder/ S- S-CDWT- Pulp/ Synth. Binder Co- BW Thick. CDWT CDWT M Synth.Type % binder (gsm) (mm) (kg/3″) (kg/3″) (kg/3″) 100/0  None 20% F/360.28 1.18 0.687 0 0 85/15 PET 20% F/3 62.90 1.25 0.660 0 0 6 mm 75/25PET 20% F/3 59.32 1.19 0.805 0 0.170 6 mm 75/25 PET 20% F/3 60.65 1.480.790 0 0.120 6 mm 85/15 PET 20% F/3 62.67 1.46 0.757 0 0 6 mm 85/15Lyocell- 19% F/2 58.3 1.08 0.969 0 0 6 mm 75/25 Lyocell- 19% E/2 59.21.09 1.080 0 0.127 6 mm

The non-zero soaked CDWT tensiles in 200 ppm of divalent cation arenon-zero for those trial combinations with 25% synthetic fiber (PET orLyocell), suggesting that higher amounts can begin to compromise waterdispersibility.

EXAMPLE 28

The substrates shown in Table 23 were all made according to the methodsof Example 10 and prepared according to the methods described in Example23. All of the substrates in Table 23 were formed from airlaid pulp(CF405). All binder blends were 75% SSB and 25% co-binder. The drythickness of the sheet was controlled by adjusting the level of webcompaction by the two compaction rolls prior to the first sprayapplication of binder. SSB Codes O and Q from Table 15 were used.

TABLE 23 Data for substrates with PET fibers and various co-binders. %Binder Binder/ BW Thick. CDWT S-CDWT S-CDWT-M in sheet Cob. (gsm) (mm)(kg/3″) (kg/3″) (kg/3″) 20 O/1 66.0 1.27 1.055 0 0 20 O/1 68.2 0.771.550 0 0 20 O/1 52.5 1.19 0.728 0 0 20 Q/1 54.19 0.75 1.372 0 0 17 Q/157.5 0.89 1.110 0 0 20 Q/1 59.90 0.75 1.583 0 0 20 Q/1 65.36 0.76 1.6960 0 20 Q/1 66.43 1.20 1.296 0 0

It appears that compaction of the dry web prior to binder applicationcan significantly increase final sheet wet strength without sacrificingdispersibility. This unexpected level of strength increase can allowequivalent wet tensiles to be achieved in a variety of combinationsincluding basis weight reduction and/or percent binder in sheetreductions.

EXAMPLE 29

All substrates were prepared according to the methods described inExample 27. All substrates were comprised of the fiber blend noted inTable 24 with 20% binder in the sheet and Dur-O-Set RB serving as theco-binder. Synthetic fibers were crimped and either 6 mm PET (KoSa) or 6or 8 mm Lyocell with 1.7 or 2.4 dtex (Accordis).

TABLE 24 Data for substrates with various fibers and binders. % S-S-CDWT- Syn. Syn. Binder/ SSB BW Thick. CDWT CDWT M Code Fiber FiberCob. MW (gsm) (mm) (kg/3″) (kg/3″) (kg/3″) 2701 0 none F/1 545000 59.81.06 0.735 0 0 2702 15 PET F/1 545000 63.3 1.31 0.782 0 0 2713 15 L-2.4-F/1 545000 62.0 1.39 0.840 0 0 6 2714 15 L-1.7- F/1 545000 61.8 1.330.768 0 0 6 2715 15 L-1.7- F/1 545000 63.7 1.47 0.842 0 0 8 2716 0 noneJ/1 710000 65.5 1.11 1.193 0 0 2717 15 L-1.7- J/1 710000 61.4 1.02 1.5120 0.200 8 3010 0 none R/1 638000 61.10 0.80 1.710 0 0 3015 15 PET R/1638000 62.23 0.86 1.769 0 0.070 3016 5 L-1.7- R/1 638000 60.63 0.792.620 0 0.170 8

The examples of Table 24 suggest that that synthetic fiber length, SSBmolecular weight and web compaction in combination can affect thedispersibility of the product as indicated by its S-CDWT-M value. Allsubstrates comprised of the 6 or 8 mm synthetic fibers were dispersiblewith the lower molecular weight SSB. As the molecular weight wasincreased, the 8 mm Lyocell substrate began to retain some of itsstrength after soaking for 1 hour in the divalent cation solution; thissubstrate, however, was dispersible in DI water. Densifying the dry webprior to binder application can also impact the dispersibility of asynthetic fiber containing substrate (Codes 3015 and 3016). Both Code3015 and Code 3016 were fully dispersible in the DI water. Sheetdispersibility can be managed by choosing lower molecular weight SSBs incombination with synthetic fibers and dry web densification.

EXAMPLE 30

The substrates listed in Table 25 were prepared, wetted with 4% NaClsolution, and tested according to the methods described in Example 29.Each substrate was comprised of the fiber blend noted and 20% binderwith the SSB/co-binder blend noted in Table 25. Dur-O-Set RB was theco-binder used in all of the samples listed in Table 25. All codes used100% softwood fiber except the last one, Code 2813, which comprised 15%PET fiber (the 6 mm, crimped fiber obtained from KoSa). Basis weight wasgenerally held constant to about 60 gsm. The thickness of the airlaidweb was controlled by adjusting the level of web compaction by the twocompaction rolls prior to the first spray application of binder. The dryCD stiffness of selected substrates in Table 25 were measured using aHandle-o-meter and reported as stiffness.

TABLE 25 Data for substrates with various binder blends. Binder/ Bind.BW Thick. CDWT S-CDWT S-CDWT-M Stiffness Code Cob. Type (gsm) (mm)(kg/3″) (kg/3″) (kg/3″) g force 3025 100/0  R 58.42 1.23 1.003 0 0 2003026 100/0  R 58.68 0.76 1.953 0 0 214 3007 75/25 R 60.23 1.19 0.942 0 0189 3008 75/25 R 59.38 1.03 1.161 0 0 3009 75/25 R 59.73 0.92 1.243 0 03010 75/25 R 61.10 0.80 1.713 0 0 181 3021 65/35 R 62.24 1.17 0.988 00.050 177 3022 65/35 R 62.07 0.81 1.800 0.030 0.200 167 3024 55/45 R58.95 1.23 0.853 0 0.100 145 3023 55/45 R 59.01 0.78 1.608 0.150 0.230141 2812 65/35 P 59.1 1.37 0.735 0 0 2813 65/35 P 59.4 1.41 0.723 0 0

As the percentage of the salt sensitive binder in the blend is decreasedfrom 100% to 55% there is only to modest decrease in the CDWT atconstant dry bulk. At compositions of 65% salt-sensitive binder in thebinder blend, the substrate begins to retain a greater portion of itswet strength after soaking for 1 hour in 200 ppm of the divalent cationsolution. As the web is densified prior to the first binder applicationand the percentage of salt sensitive binder in the blend is reduced to65% or lower, a greater amount of strength is retained after soaking inDI water or the 200 ppm divalent cation solution for 1 hour compared tothe same compositions at a higher dry bulk. These examples suggest thatincreasing the co-binder content with or without additionaldensification of the web can begin to compromise substratedispersibility.

The results in Table 25 also show significant CDWT increases as thethickness of the dry web is compressed prior to the application of thebinder. Codes 3007 to 3010 show that the CDWT is increasing as afunction of decreasing dry bulk with no loss of substrate dispersibilityat constant binder conditions.

Based on the Handle-O-Meter results (stiffness), it appears that as thepercentage of salt sensitive binder in the blend is decreased, the CDstiffness of the substrate decreases.

EXAMPLE 31

The substrates listed in Table 26 were prepared according to the methoddescribed in Examples 10 and 23. Each substrate comprised pulp (CF405)and 20% binder. The binder had the SSB/co-binder blend given in Table26. Dur-O-Set RB was the co-binder. The substrate was converted intoroll form and wetted with solution Q of Table 19 (solution D).Measurements were made of the peel force required to unroll the productfrom the outer layers of the coreless roll of pre-moistened wipesaccording to the method described in Example 25. The results of thesetests are recorded in Table 26 below.

TABLE 26 Peel force results for coreless rolls. % Binder Binder Binder/BW Thick. Peel Code In sheet Blend Cob. (gsm) (mm) (g) 3026 20 100/0 R/1 58.68 0.76 142 3010 20 75/25 R/1 61.10 0.80 139 3022 20 65/35 R/162.07 0.81 116 3023 20 55/45 R/1 59.01 0.78 111

In this case, decreasing the percentage of the salt-sensitive binder inthe blend decreased the peel force.

EXAMPLE 32

Samples were made as in Example 10 using 75/25 blends of SSB Table 15)and Dur-O-Set RB co-binder (co-binder 1 of Table 16), according to theinformation in Table 27 below. Tensile results in Table 27 show gooddispersibility over a range of product conditions.

TABLE 27 Tensile results for a range of binders and basesheetproperties. % Binder/ SSB BW Thick. CDWT S-CDWT S-CDWT-M Binder Cob. MW(gsm) (mm) (kg/3″) (kg/3″) (kg/3″) 20 O/I 632000 52.5 1.19 0.728 0 0 20Q/I 575000 54.19 0.75 1.372 0 0 15.2 J/1 710000 55.2 1.47 0.320 0 0 24L/1 834000 60.4 0.92 1.070 0 0 20 D/1 548000 62.5 1.32 0.900 0 0 20 H/1790000 63.1 1.3 1.070 0 0 22 R/1 638000 66.47 0.76 2.273 0 0 20 C/1604,000 74.4 1.47 1.120 0 0

The samples reported in Table 27 demonstrate some of the ranges ofbinder content, basis weight, and web thickness over which dispersiblesubstrates can be made.

EXAMPLE 33

Samples were made generally as in Example 10 using 75/25 blends of SSBbinder (see Table 15) and co-binder (see Table 16) as noted in Table 28.All substrates contain 6 mm crimped, 2.4 dtex Lyocell (Accordis) as 15%of the fiber blend with 85% softwood pulp (CF405). All substrates arecomprised of 19% binder and 81% of the binder blend.

TABLE 28 Tensile results for a range of binders and basesheetproperties. Binder/ SSB BW Thick. CDWT S-CDWT S-CDWT-M Cob. MW. (gsm)(mm) (kg/3″) (kg/3″) (kg/3″) L/1 845,000 61.1 1.17 0.960 0 0 W/1 734,00060.2 1.17 0.960 0 0.198 AB/1 544,000 56.2 0.95 1.060 0 0 AB/2 544,00058.6 1.06 0.990 0 0.205 E/2 609,000 58.3 1.08 0.969 0 0

In Table 28, all samples lost at least 75% of their wet strength aftersoaking in the 200 ppm divalent cation solution for 1 hour (S-CDWT-M).The main differences in these samples is in the SSB composition, asdepicted in Table 15. Salt-sensitive binders L and E have the samecomposition, but different molecular weights, than the salt sensitivebinders W and AB (see Table 15). Salt sensitive binders W and AB havethe same composition but different molecular weights. The W/1- andAB/2-treated substrates appear to be less dispersible than the L/1- andE/2-treated substrates independently of co-binder. Reducing the saltsensitive binder's molecular weight can be used to make the substratemore dispersible as is shown by substrate AB/1. Or, changing the saltsensitive binder's composition can be used to make the substrate moredispersible as demonstrated by L/1 and E/2. Thus, by modifying the saltsensitive binder's molecular composition or its molecular weight, fullydispersible blends can be made. Alternatively, by selecting a differentco-binder chemistry to be more compatible with the salt sensitivebinder, fully dispersible binder blends can be made as demonstrated bysubstrates AB/2 and AB/1.

EXAMPLE 34

A latex emulsion comprising about 6% NMA crosslinker, AirFlex 105 (AirProducts, Allentown, Pa.), was combined with SSB Code H of Table 15 at aratio of 75 parts SSB to 25 parts latex solids and cast into 8 bars withdimensions 1 cm×4 cm×3 mm as described in Example 9. Four bars wereprepared by drying in air at 60° C. overnight, while the other four barswere dried at 167° C. for 3 hours. Two bars from each set were then eachplaced in 30 ml of 4% NaCl solution and allowed to sit for one hour,after which solubility was determined gravimetrically. Bars from bothsets (the two drying conditions) were essentially completely insolublein the saline solution. The remaining bars from each set were eachplaced in 30 ml of hard water containing 200 ppm calcium and magnesiumions at a 2:1 ratio at about 23° C. and allowed to sit for one hour. Thetwo bars dried at 167° C. and placed in hard water were essentiallycompletely insoluble (0% soluble). The two bars dried at 60° C. andplaced in hard water were 54% and 53% soluble, respectively, which wasunexpectedly low given that the latex should be substantiallyuncrosslinked for drying at this temperature. However, some coagulationoccurred when the latex was mixed with the SSB, suggesting a possiblecompatibility problem between the two mixtures, and thus solubility maybe impaired, or some coagulated particles may not have passed throughthe filter paper. It is also possible that some of the NMA crosslinkerin the Airflex latex may have promoted crosslinking or gelling of theblend. While it is believed that a more compatible latex emulsion wouldhave yielded higher solubility, it is also believed that co-binders thatare relatively low in crosslinking agents (e.g., less than 6%,specifically less than 2%, more specifically less than 1%, and mostspecifically less than 0.3% crosslinker on a solids mass basis) can behelpful in maintaining high solubility of the dried polymer blend.

FIG. 1 shows the wet tensile results for treated airlaid basesheets,wherein the tests have been carried out in different saline solutions orhard water. The airlaid basesheets were prepared according to Example 10and provided with 20% add-on of salt-sensitive binder compositionslabeled as Code X, Code Y, and Code Z. Code X is a binder polymercomprising 60% acrylic acid, 10.5% 2-ethylhexyl acrylate, 24.5% butylacrylate, and 5% NaAMPS, polymerized according to Example 1 with amolecular weight of 1.3 million, corresponding to Code B in Table 15.Code Y is similar but with a molecular weight of about 550,000,corresponding to Code D in Table 15. Code Z is similar but has 62%acrylic acid and 8.5% 2-ethylhexyl acrylate as monomers, with amolecular weight of about 1.2 million, corresponding to Code G in Table15. All binders were blended with Dur-O-Set RB co-binder in a 75:25ratio. The treated webs were dried, as in Example 10, and then wettedwith either a 4% or 1.5% NaCl solution. Wet tensile testing wasconducted according to the CDWT protocol with the exceptions describedin Example 5 (e.g., a 1-inch wide strip and a MTS tensile tester wereused).

Soaked CD tensile tests were conducted on samples prepared with the 4%solution. The four columns shown for each code (some of which are notvisible due to zero values) correspond to the results from the fourdifferent tests. The first two columns are the CDWT values “as is” forthe web in either the 4% or 1.5% NaCl solution. The third and fourthcolumns are the S-CDWT-M (hard water soak) results at 1 hour and 3 hoursfor each web that had been wetted with the 4% solution.

The results show good wet strength at both 1.5% NaCl and 4% NaCl, withexcellent strength loss for webs treated with Code Y (Hard WaterDispersibility of 100%), good strength loss for Code Z, and residualstrength still present for Code X. Comparison of Code X to Code Ysuggests that a reduction in molecular weight can promote dispersibilityof the salt-sensitive binder.

FIG. 2 is a chart showing how wet tensile strength (reported as CDWT ingrams per 2.54 cm over a range of soak times) can change over time as 68gsm softwood airlaid webs comprising ion-sensitive binders are soaked insolutions comprising calcium ions. The moistened webs were prepared with20% binder by weight comprising 85% Lion (Tokyo, Japan) SSB-3bacrylic-acid based terpolymer and 15% Dur-O-Set RB (National Starch)co-binder. After being dried, the webs were wetted with a solutioncontaining 0.9% NaCl, 0.5% phospholipid CDM (Mona), and 0.5% MackstatH-66 and displayed a wet strength of about 400 g/in (or g/2.54 cm).Solution add-on was 250% based on the dry weight of the web. The treatedwebs were then soaked in NaCl-free water containing calcium ions atlevels of 0, 13, 29, and 109 ppm, yielding the four curves shown in FIG.2 for wet tensile strength versus time. At 109 ppm calcium ions there isessentially no loss in strength. Strengths over 100 g/in are maintainedin 29 ppm calcium ions. It appears that even a small amount of calciumions in the water will interfere with a dispersibility of a web treatedwith the Lion SSB-3b product. FIG. 3 compares two data sets with LionSSB-3b product taken from FIG. 2 (labeled as Code 3300) with asulfonated salt-sensitive binder blended with Dur-O-Set RB polymer in a75/25 ratio. The data set labeled as Code 2102 refers to a 65-gsm webcontaining the sulfonated salt-sensitive binder, which corresponds toSSB Code H in Table 15. This web was wetted with the solution describedin Table 4. Solution add-on was 225% based on the dry weight of the web.This binder formulation displayed a rapid drop in tensile strength—hencegood triggerability—when immersed in hard water, even at a calcium ionconcentration of 257 ppm. Thus, the sulfonated salt-sensitive binders ofthe present invention show a dramatic improvement in their ability to bedispersible in hard water relative to prior acrylic-acid basedterpolymers.

Tensile results for data in FIG. 2 and FIG. 3 were obtained with an MTStensile test devices, the MTS 500/S unit (MTS Systems, Research Park,N.C.) using the Testworks™ 3.10 for Windows software. Instead of thenormal 3-inch strip for testing, a 1-inch wide strip was used, cut to 6inches in length. The gauge length between the rubber-coated jaws of thetest device was 3 inches. Testing was operated at the specifiedcrosshead speed of 12 in/min.

It should be understood, of course, that the foregoing relates only tocertain disclosed embodiments of the present invention and that numerousmodifications or alterations may be made therein without departing fromthe spirit and scope of the invention as set forth in the appendedclaims.

What is claimed is:
 1. A fibrous substrate comprising: fibrous material;and a binder composition for binding said fibrous substrate into anintegral web, said binder composition comprising a sulfonate anionmodified acrylic acid terpolymer and a non-crosslinkingpoly(ethylene-vinyl acetate), wherein the binder composition isinsoluble in a neutral salt solution containing at least about 1 weightpercent salt, said salt comprising one or more monovalent ions; andwherein the binder composition is dispersible in water containing up toabout 200 ppm of one or more multivalent ions.
 2. The fibrous substrateof claim 1, wherein the binder composition is dispersible in watercontaining from about 15 ppm to about 200 ppm of one or more multivalentions.
 3. The fibrous substrate of claim 1, wherein the bindercomposition is dispersible in water containing from about 15 ppm toabout 150 ppm of one or more multivalent ions.
 4. The fibrous substrateof claim 1, wherein the binder composition is dispersible in watercontaining from about 15 ppm to about 100 ppm of one or more multivalentions.
 5. The fibrous substrate of claim 1, wherein the bindercomposition is dispersible in water containing from about 15 ppm toabout 50 ppm of one or more multivalent ions.
 6. The fibrous substrateof claim 1, wherein the binder composition is dispersible in watercontaining less than about 10 ppm of one or more multivalent ions. 7.The fibrous substrate of claim 1, wherein the binder composition isinsoluble in a neutral salt solution containing from about 1 weightpercent to about 5.0 weight percent salt.
 8. The fibrous substrate ofclaim 1, wherein the binder composition is insoluble in a neutral saltsolution containing from about 1 weight percent to about 3.0 weightpercent salt.
 9. The fibrous substrate of claim 1, wherein themultivalent ions comprise Ca²⁺ ions, Mg²⁺ ions, Zn²⁺ ions, or acombination thereof.
 10. The fibrous substrate of claim 1, wherein themonovalent ions comprise Na⁺ ions, Li⁺ ions, K⁺ ions, NH₄ ⁺ ions, or acombination thereof.
 11. The fibrous substrate of claim 1, wherein theacrylic acid terpolymer comprises at least one of acrylic acid andmethacrylic acid, and one or more alkyl acrylates.
 12. The fibroussubstrate of claim 1, wherein the sulfonate anion modified acrylic acidterpolymer is formed from at least four monomers selected from acrylicacid; 2-acrylamido-2-methyl-1-propanesulfonic acid and the alkali earthmetal and organic amine salts thereof; butyl acrylate; and 2-ethylhexylacrylate.
 13. The fibrous substrate of claim 1, wherein the sulfonateanion modified acrylic acid terpolymer is formed from at least fourmonomers selected from acrylic acid; AMPS; NaAMPS; butyl acrylate; and2-ethylhexyl acrylate.
 14. The fibrous substrate of claim 1, wherein thesulfonate anion modified acrylic acid terpolymer comprises from about 35to less than 80 mole percent acrylic acid; from greater than 0 to about20 mole percent 2-acrylamido-2-methyl-1-propanesulfonic acid and alkaliearth metal and organic amine salts thereof; from greater than 0 toabout 65 mole percent butyl acrylate; and from greater than 0 to about45 mole percent 2-ethylhexyl acrylate.
 15. The fibrous substrate ofclaim 1, wherein the sulfonate anion modified acrylic acid terpolymercomprises from about 50 to less than 67 mole percent acrylic acid; fromgreater than 0 to about 10 mole percent2-acrylamido-2-methyl-1-propanesulfonic acid and alkali earth metal andorganic amine salts thereof; from about 15 to about 28 mole percentbutyl acrylate; and from about 7 to about 15 mole percent 2-ethylhexylacrylate.
 16. The fibrous substrate of claim 1, wherein the sulfonateanion modified acrylic acid terpolymer comprises from about 57 to lessthan 66 mole percent acrylic acid; from about 1 to about 6 mole percent2-acrylamido-2-methyl-1-propanesulfonic acid and alkali earth metal andorganic amine salts thereof; from about 15 to about 28 mole percentbutyl acrylate; and from about 7 to about 13 mole percent 2-ethylhexylacrylate.
 17. The fibrous substrate of claim 1, wherein the bindercomposition comprises from about 65 to about 75 weight percent of thesulfonate anion modified acrylic acid terpolymer.
 18. The fibroussubstrate of claim 1, wherein the binder composition comprises fromabout 55 to 99 weight percent of the non-crosslinkingpoly(ethylene-vinyl acetate).
 19. The fibrous substrate of claim 1,wherein the binder composition comprises from about 25 to about 35weight percent of the non-crosslinking poly(ethylene-vinyl acetate). 20.The fibrous substrate of claim 1, wherein the sulfonate anion modifiedacrylic acid terpolymer comprises from about 57 to less than 66 molepercent acrylic acid; from about 1 to about 6 mole percent AMPS orNaAMPS; from about 15 to about 28 mole percent butyl acrylate; and fromabout 7 to about 13 mole percent 2-ethylhexyl acrylate; and wherein thebinder composition comprises from about 65 to 75 weight percent of thesulfonate anion modified acrylic acid terpolymer and from about 25 to 35weight percent of the non-crosslinking poly(ethylene-vinyl acetate). 21.The fibrous substrate of claim 1, wherein the fibrous material comprisesone or more layers of a woven fabric, a nonwoven fabric, a knittedfabric, or a combination thereof.
 22. The fibrous substrate of claim 1,wherein the fibrous material comprises one or more layers of a nonwovenfabric.
 23. The fibrous substrate of claim 1, wherein the fibrousmaterial comprises fibers having a length of about 15 mm or less. 24.The fibrous substrate of claim 1, wherein the fibrous material comprisesnatural fibers, synthetic fibers, or a combination thereof.
 25. Thefibrous substrate of claim 1, wherein the fibrous material comprises oneor more fibers containing cotton, linen, jute, hemp, wool, wood pulp,viscose rayon, cuprammonium rayon, cellulose acetate, polyester,polyamide, and polyacrylic.
 26. The fibrous substrate of claim 1,wherein the fibrous material comprises wood pulp.
 27. A fibroussubstrate comprising: fibrous material; and a binder composition forbinding said fibrous material into an integral web, said bindercomposition comprising a first polymer formed from at least fourmonomers selected from acrylic acid,2-acrylamido-2-methyl-1-propanesulfonic acid and alkali earth metal andorganic amine salts thereof, butyl acrylate, and 2-ethylhexyl acrylate;and a second polymer comprising a non-crosslinking poly(ethylene-vinylacetate); wherein the binder composition is insoluble in a neutral saltsolution containing at least about 1 weight percent salt, said saltcomprising one or more monovalent ions; and wherein the bindercomposition is dispersible in water containing up to about 200 ppm ofone or more multivalent ions.
 28. The fibrous substrate of claim 27,wherein the first polymer comprises from about 35 to less than 80 molepercent acrylic acid; from greater than 0 to about 20 mole percent2-acrylamido-2-methyl-1-propanesulfonic acid and alkali earth metal andorganic amine salts thereof; from greater than 0 to about 65 molepercent butyl acrylate; and from greater than 0 to about 45 mole percent2-ethylhexyl acrylate.
 29. The fibrous substrate of claim 27, whereinthe first polymer comprises from about 50 to less than 67 mole percentacrylic acid; from greater than 0 to about 10 mole percent2-acrylamido-2-methyl-1-propanesulfonic acid and alkali earth metal andorganic amine salts thereof; from about 15 to about 28 mole percentbutyl acrylate; and from about 7 to about 15 mole percent 2-ethylhexylacrylate.
 30. The fibrous substrate of claim 27, wherein the firstpolymer comprises from about 57 to less than 66 mole percent acrylicacid; from about 1 to about 6 mole percent2-acrylamido-2-methyl-1-propanesulfonic acid and alkali earth metal andorganic amine salts thereof; from about 15 to about 28 mole percentbutyl acrylate; and from about 7 to about 13 mole percent 2-ethylhexylacrylate.
 31. The fibrous substrate of claim 27, wherein the firstpolymer is present in an amount from about 65 to about 75 weightpercent.
 32. The fibrous substrate of claim 27, wherein the secondpolymer is present in an amount from about 1 to 45 weight percent. 33.The fibrous substrate of claim 29, wherein the binder compositioncomprises from about 25 to about 35 weight percent non-crosslinkingpoly(ethylene-vinyl acetate).
 34. The fibrous substrate of claim 27,wherein the first polymer comprises from about 57 to less than 66 molepercent acrylic acid; from about 1 to about 6 mole percent AMPS orNaAMPS; from about 15 to about 28 mole percent butyl acrylate; and fromabout 7 to about 13 mole percent 2-ethylhexyl acrylate; and wherein thebinder composition comprises from about 65 to about 75 weight percent ofthe first polymer and from about 25 to about 35 weight percent of thesecond polymer.
 35. The fibrous substrate of claim 27, wherein thebinder composition is insoluble in a neutral monovalent salt solutioncontaining from about 1 weight percent to about 5.0 weight percent ofthe salt.
 36. The fibrous substrate of claim 27, wherein the fibrousmaterial comprises one or more layers of a woven fabric, a nonwovenfabric, a knitted fabric, or a combination thereof.
 37. The fibroussubstrate of claim 27, wherein the fibrous material comprises one ormore layers of a nonwoven fabric.
 38. The fibrous substrate of claim 27,wherein the fibrous material comprises fibers having a length of about15 mm or less.
 39. The fibrous substrate of claim 27, wherein thefibrous material comprises natural fibers, synthetic fibers, or acombination thereof.
 40. The fibrous substrate of claim 27, wherein thefibrous material comprises one or more fibers containing cotton, linen,jute, hemp, wool, wood pulp, viscose rayon, cuprammonium rayon,cellulose acetate, polyester, polyamide, and polyacrylic.
 41. Thefibrous substrate of claim 27, wherein the fibrous material compriseswood pulp.
 42. A water-dispersible article comprising the fibroussubstrate of claim
 1. 43. A water-dispersible article comprising thefibrous substrate of claim
 27. 44. A fibrous substrate comprising:fibrous material; and a binder composition for binding said fibrousmaterial into an integral web, said binder composition comprising afirst polymer formed from three monomers: acrylic acid, butyl acrylate,and 2-ethylhexyl acrylate and a second polymer selected fromnon-crosslinking poly(ethylene-vinyl acetate), non-crosslinkingpoly(styrene-butadiene), and non-crosslinking poly(styrene-acrylic),wherein the binder composition is insoluble in a neutral salt solutioncontaining at least about 1 weight percent salt, said salt comprisingone or more monovalent ions; and wherein the polymer is dispersible inwater containing up to about 200 ppm of one or more multivalent ions.45. A water-dispersible article comprising the fibrous substrate ofclaim
 44. 46. A fibrous substrate comprising: fibrous material; and abinder composition for binding said fibrous substrate into an integralweb, said binder composition comprising a sulfonate anion modifiedacrylic acid terpolymer and a co-binder dispersed in the terpolymer,wherein the binder composition is insoluble in a neutral salt solutioncontaining at least about 1 weight percent salt, said salt comprisingone or more monovalent ions; and wherein the binder composition isdispersible in water containing up to about 200 ppm of one or moremultivalent ions.